Methods and apparatus for data exchange in peer to peer communications

ABSTRACT

An exemplary wireless communications device comprises a processor coupled to a memory and a wireless communications interface. The processor is configured to transmit a first transmission symbol at a first time index from a first set of time indices, and to transmit a second transmission symbol at a second time index different from the first time index from the first set of time indices, a portion of the first transmission symbol and a portion of the second transmission symbol including the same data. The first set of time indices is associated with a first device ID and includes at least one time index not contained in a second set of time indices associated with a second device ID, and the second set includes at least one time index not contained in the first set.

RELATED APPLICATIONS

The present Application for patent claims priority to ProvisionalApplication No. 60/948,980 entitled “METHODS AND APPARATUS FOR DATAEXCHANGE IN PEER TO PEER COMMUNICATIONS” filed Jul. 10, 2007, andassigned to the assignee hereof and hereby expressly incorporated byreference herein.

FIELD

Various embodiments are directed to methods and apparatus for wirelesscommunication and, more particularly, to methods and apparatus relatedto peer to peer communications.

BACKGROUND

In a wireless network, in which a network infrastructure does not exist,such as an ad hoc peer to peer network, a terminal is faced with anumber of challenges when establishing a communication link with anotherpeer terminal. One challenge is that when a terminal just powers up ormoves into a new area, the terminal may have to first find out whetheranother terminal is present in the vicinity before any communicationbetween the two terminals can start.

The general solution to the above problem of identification andacquisition is to let the terminal transmit and/or receive signalsaccording to a communication protocol. However, an ad hoc networkpresents a number of challenges. Often the terminals may not have acommon timing reference, e.g., because of the lack of the networkinfrastructure. As such, it is possible that when a first terminal istransmitting a signal and a second terminal is not in the receivingmode, the transmitted signal does not help the second terminal to detectthe presence of the first terminal.

Half-duplex terminals present another challenge in that they areincapable of transmitting and receiving simultaneously. In such case,each of two terminals could be transmitting a message at the same timeand may not be able to detect the presence of the other terminal becauseit could not receive the other terminal's signal at the time it istransmitting. These issues not only impact peer detection, but alsoimpact other communications such as user scheduling, among others.

Finally, power efficiency has great impact on the battery life of theterminals and is thus another important consideration in any wirelesssystem.

SUMMARY

Devices, systems and methods are described herein that addresses one ormore of the shortcomings described above. An exemplary wirelesscommunications device comprises a processor coupled to a memory and awireless communications interface. The processor is configured totransmit a first transmission symbol at a first time index from a firstset of time indices, and to transmit a second transmission symbol at asecond time index, which is also from the first set of time indices butis different from the first time index from the first set of timeindices, a portion of the first transmission symbol and a portion of thesecond transmission symbol including the same data. For example, thefirst transmission symbol and the second transmission symbol may bebeacon-type signals which occupy a small frequency bandwidth or aspread-spectrum signal which occupies a large portion of the availablebandwidth. The first set of time indices is associated with a firstdevice ID and includes at least one time index not contained in a secondset of time indices associated with a second device ID, and the secondset includes at least one time index not contained in the first set.According to one aspect, a table stored in the memory maps the firstdevice ID to the first set of time indices and the second device ID to asecond set of time indices. According to another aspect, the processorexecutes a function to map the first device ID to the first set of timeindices and the second device ID to the second set of time indices.

According to another aspect, the processor executes a module thatdetermines the current device ID used by the device at the present timeto be one of at least the first and the second device ID, maps thecurrent device ID to one of at least the first and the second sets oftime indices, and transmits a transmission symbol at a time index fromthe mapped set of time indices. Varying the device ID assigned to a nodein the manner reduces potential desense effects from other devices inthe network.

According to one aspect, the first set of time indices and the secondset of time indices are of the same size. According to anther aspect thefirst set of time indices has a size equal to the closest integer tohalf of the size of the transmission block interval for transmission.

By way of illustration, the first transmission symbol may be modulatedin a CDMA waveform or an OFDM waveform. As described below, the size ofthe first set of time indices may be determined by the size of thedevice ID space (i.e., the number of mobile nodes supported) and themaximum number of CDMA waveforms supportable in a given time index wherethe modulation technique is a CDMA waveform. Similarly, the size of thefirst of time indices may also determined by at least the size of thedevice ID space and the maximum number of frequency indices supportablein the system where the modulation technique is an OFDM waveform.

According to one aspect, the processor is configured to transmit thefirst transmission symbol at a first frequency index, and to transmitthe second transmission symbol at a second frequency index, differentfrom the first frequency index. In one particular aspect describedbelow, the first frequency index=i, the first time index=j, the secondfrequency index=j, the first time index=i.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates an exemplary ad hoc communication networkimplemented.

FIG. 2 illustrates an exemplary user misdetection problem in an ad hocnetwork when there is no common timing reference.

FIG. 3 illustrates an exemplary air link resource being used tocommunicate a beacon signal including three exemplary beacon signalbursts, each beacon signal burst including one beacon symbol.

FIG. 4 illustrates an exemplary relative transmission power levelsbetween a beacon symbol and a data/control signal.

FIG. 5 illustrates one exemplary embodiment of transmitting beaconsignal bursts.

FIG. 6 illustrates one exemplary embodiment in which receiving beaconsignal bursts can occur during certain designated time intervals, whileat other times the receiver is off to conserve power.

FIG. 7 is used to describe how a user misdetection problem is solvedwhen two terminals transmit and receive beacon signal bursts, asimplemented.

FIG. 8 illustrates one exemplary embodiment of a state diagramimplemented in a terminal.

FIG. 9 illustrates a detailed illustration of an exemplary wirelessterminal implemented.

FIG. 10 is a drawing of a flowchart of an exemplary method of operatinga portable wireless terminal.

FIG. 11 is a drawing of a flowchart of an exemplary method of operatinga portable wireless terminal.

FIG. 12 is a drawing of a flowchart of an exemplary method of operatinga portable wireless terminal, e.g., a battery powered mobile node.

FIG. 13 is a drawing of a flowchart of an exemplary method of operatinga portable wireless terminal, e.g., a battery powered mobile node.

FIG. 14 includes drawings illustrating exemplary beacon signaling from aportable wireless terminal.

FIG. 15 illustrates that different wireless terminals, transmitdifferent beacon signals including different beacon burst signals.

FIG. 16 is a drawing and corresponding legend illustrating a feature ofsome embodiments, in which a beacon symbol transmission unit includes aplurality of OFDM symbol transmission units.

FIG. 17 is a drawing used to illustrate an exemplary beacon signalcomprising a sequence of beacon burst signals and to illustrate timingrelationships of some embodiments.

FIG. 18 is a drawing used to illustrate an exemplary beacon signalcomprising a sequence of beacon burst signals and to illustrate timingrelationships of some embodiments.

FIG. 19 is a drawing illustrating exemplary air link resourcepartitioning by a wireless terminal in a mode of operation in which thewireless terminal transmits a beacon signal.

FIG. 20 describes an exemplary air link resource portion associated withuses other than beacon signal transmission for an exemplary mode ofwireless terminal operation in which the wireless terminal transmits abeacon signal and can receive and/or transmit user data, e.g., an activemode of operation.

FIG. 21 illustrates two exemplary modes of wireless terminal operationin which the wireless terminal is transmitting a beacon signal, e.g., aninactive mode and an active mode.

FIG. 22 includes a drawing and corresponding legend illustratingexemplary wireless terminal air link resource utilization during anexemplary first time interval including two beacon bursts.

FIG. 23 includes a drawing and corresponding legend illustratingexemplary wireless terminal air link resource utilization during anexemplary first time interval including two beacon bursts.

FIG. 24 illustrates an alternative descriptive representation withrespect to beacon signals.

FIG. 25 is a drawing of an exemplary portable wireless terminal, e.g.,mobile node.

FIG. 26 is a drawing of a flowchart of an exemplary method of operatinga communications device, e.g., a battery powered wireless terminal.

FIG. 27 is a drawing of an exemplary portable wireless terminal, e.g.,mobile node.

FIG. 28 is a drawing illustrating an exemplary time line, sequence ofevents, and operations with respect to two wireless terminals in an adhoc network which become aware of the presence of each other and achievetiming synchronization via the use of wireless terminal beacon signals.

FIG. 29 illustrates exemplary synchronized timing between two wirelessterminals based on beacon signals in accordance with an exemplaryembodiment.

FIG. 30 illustrates exemplary synchronized timing between two wirelessterminals based on beacon signals in accordance with another exemplaryembodiment.

FIG. 31 illustrates exemplary synchronized timing between two wirelessterminals based on beacon signals in accordance with another exemplaryembodiment.

FIGS. 32 and 33 illustrate exemplary data exchange arrangements inaccordance with exemplary embodiments.

FIGS. 34 and 35 illustrate exemplary slot assignment arrangements for aplurality of nodes in accordance with exemplary embodiments.

FIG. 36 illustrates an exemplary table indentifying time and frequencyresource assignment arrangement in accordance with an exemplaryembodiment.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary ad hoc communication network 100implemented. Two exemplary wireless terminals, namely a first wirelessterminal 102 and a second wireless terminal 104 are present in ageographic area 106. Some spectrum band is available to be used by thetwo wireless terminals for the purpose of communication. The twowireless terminals use the available spectrum band to establish apeer-to-peer communication link between each other.

Because the ad hoc network may not have a network infrastructure, thewireless terminals may not have a common timing or frequency reference.This results in certain challenges in the ad hoc network. To elaborate,consider the problem of how either of the terminals detects the presenceof the other.

For the sake of description, in the following it is assumed that at agiven time, the wireless terminal can either transmit or receive, butnot both. It is understood that people with ordinary skills in the fieldcan apply the same principles to the case where the terminal can bothtransmit and receive at the same time.

FIG. 2 includes drawing 200 used to describe one possible scheme thatthe two wireless terminals may use to find each other. The firstterminal transmits some signal in time interval 202, and receives signalin time interval 204. Meanwhile, the second wireless terminal transmitssome signal in time interval 206, and receives signal in time interval208. Note that if the first wireless terminal can both transmit andreceive at the same time then the time intervals 202 and 204 may overlapwith each other.

Note that because the two terminals do not have a common timingreference, their TX (transmit) and RX (receive) timings are notsynchronized. In particular, FIG. 2 shows that the time intervals 204and 206 do not overlap. When the first wireless terminal is listeningthe second wireless terminal does not transmit, and when the secondwireless terminal is transmitting the first wireless terminal does notlisten. Therefore, the first wireless terminal does not detect thepresence of the second terminal. Similarly, the time intervals 202 and208 do not overlap. Therefore, the second wireless terminal does notdetect the presence of the first wireless terminal either.

There are ways to overcome the above misdetection problem. For example,a wireless terminal may randomize the time interval in which the TX andRX procedure is carried out, so that over time the two wirelessterminals will detect each other probabilistically. However, the cost isthe delay and the resultant battery power consumption. In addition, thepower consumption is also determined by the power requirement in the TXand RX procedure. For example, it may require less processing power todetect one form of the signal than to detect another form.

It is a feature of various embodiments that a new signal TX and RXprocedure is implemented and used to reduce the delay of detecting thepresence of another terminal and the associated power consumption.

In accordance with various embodiments, a wireless terminal transmits aspecial signal, called a beacon signal, which occupies a small fraction,e.g., in some embodiments no more than 0.1%, of the total amount ofavailable air link communication resource. Air link communicationresources are measured in terms of minimum or basic transmission units,e.g., OFDM tone symbols in an OFDM system. Air link communicationresources can be measured in terms of degrees of freedom, where a degreeof freedom is the minimum unit of resource which can be used forcommunication. For example, in a CDMA system, a degree of freedom can bea spreading code, a time corresponding to a symbol period. In general,the degrees of freedom in a given system are orthogonal with each other.

Consider an exemplary embodiment of a frequency division multiplexingsystem, e.g., an OFDM system. In that system, information is transmittedin a symbol-by-symbol manner. In a symbol transmission period, the totalavailable bandwidth is divided into a number of tones, each of which canbe used to carry information.

FIG. 3 includes drawing 300 showing the available resource in anexemplary OFDM system. The horizontal axis 301 represents time and thevertical axis 302 represents frequency. A vertical column representseach of the tones in a given symbol period. Each small box 304represents a tone-symbol, which is the air link resource of a singletone over a single transmission symbol period. A minimum transmissionunit in the OFDM symbol is a tone-symbol.

The beacon signal includes a sequence of beacon signal bursts (308, 310,312), which are transmitted sequentially over time. A beacon signalburst includes a small number of beacon symbols. In this example, eachbeacon symbol burst (308, 310, 312) includes one beacon symbol and 19nulls. In this example, each beacon symbol is a single tone over onetransmission period. A beacon signal burst includes, beacon symbols ofthe same tone over a small number of transmission symbol periods, e.g.,one or two symbol periods. FIG. 3 shows three small black boxes, each ofwhich (306) represents a beacon symbol. In this case, a beacon symboluses the air link resource of one tone-symbol, i.e., one beacon symboltransmission unit is an OFDM tone-symbol. In another embodiment, abeacon symbol comprises one tone transmitted over two consecutive symbolperiods, and a beacon symbol transmission unit comprises two adjacentOFDM tone-symbols.

The beacon signal occupies a small fraction of the total minimumtransmission units. Denote N the total number of tones of the spectrumof interest. In any reasonably long time interval, e.g., of one or twoseconds, suppose the number of symbol periods is T. Then the totalnumber of minimum transmission units is N*T. In accordance with variousembodiments, the number of tone-symbols occupied by the beacon signal inthe time interval is significantly less than N*T, e.g., in someembodiments no more than 0.1% of N*T.

The tone of the beacon symbol in a beacon signal burst, varies (hops)from one burst to another. In accordance with various embodiments, thetone-hopping pattern of the beacon symbol is in some embodiments afunction of the wireless terminal and can be, and sometimes is, used asan identification of the terminal or an identification of the type towhich the terminal belongs. In general, information in a beacon signalcan be decoded by determining which minimum transmission units conveythe beacon symbols. For example, information can be included in thefrequency of the tone(s) of the beacon symbol(s) in a given beaconsignal burst, the number of beacon symbols in a given burst, theduration of a beacon signal burst, and/or the inter-burst interval, inaddition to the tone hopping sequences.

The beacon signal can also be characterized from the transmission powerperspective. In accordance with various embodiments, the transmissionpower of the beacon signal per minimum transmission unit is much higher,e.g., in some embodiments at least 10 dB higher, than the averagetransmission power of data and control signals per degree of freedomwhen the terminal transmitter is in an ordinary data session. Inaccordance with some embodiments, the transmission power of the beaconsignal per minimum transmission unit is at least 16 dB higher than theaverage transmission power of data and control signals per degree offreedom when the terminal transmitter is in an ordinary data session.For example, drawing 400 of FIG. 4 plots the transmission powers used ineach of the tone-symbols in a reasonably long time interval, e.g., ofone or two seconds, in which the wireless terminal is in a data session,i.e., the terminal is sending data and control information using thespectrum of interest. The order of those tone-symbols, represented bythe horizontal axis 401, is immaterial for purposes of this discussion.A small vertical rectangular 404 represents the power of individualtone-symbols conveying user data and/or control information. As acomparison, a tall black rectangular 406 is also included to show thepower of a beacon tone-symbol.

In another embodiment, a beacon signal includes a sequence of beaconsignal bursts transmitted at intermittent time periods. A beacon signalburst includes one or more (a small number) of time-domain impulses. Atime-domain impulse signal is a special signal that occupies a verysmall transmission time duration over a certain spectrum bandwidth ofinterest. For example, in a communication system where the availablebandwidth is 30 kHz, a time-domain impulse signal occupies a significantportion of the 30 kHz bandwidth for a short duration. In any reasonablylong time interval, e.g., a few seconds, the total duration of thetime-domain impulses is a small fraction, e.g., in some embodiments nomore than 0.1%, of the total time duration. Moreover, the per degree offreedom transmission power in the time interval during which the impulsesignal is transmitted is significantly higher, e.g., in some embodiments10 dB higher, than the average transmission power per degree of freedomwhen the transmitter is in an ordinary data session. The per degree offreedom transmission power in the time interval during which the impulsesignal is transmitted is at least 16 dB higher than the averagetransmission power per degree of freedom when the transmitter is in anordinary data session.

FIG. 4 shows that the transmission power may vary from one tone-symbolto another. Denote Pavg the average transmission power per tone-symbol(408). In accordance with various embodiments, the per tone-symboltransmission power of the beacon signal is much higher, e.g., at least10 dB higher, than Pavg. The per tone-symbol transmission power of thebeacon signal is at least 16 dB higher than Pavg. In one exemplaryembodiment, the per tone-symbol transmission power of the beacon signalis 20 dBs higher than Pavg.

In one embodiment, the per tone-symbol transmission power of the beaconsignal is constant for a given terminal. That is, the power does notvary with time or with tone. In another embodiment, the per tone-symboltransmission power of the beacon signal is the same for multipleterminals, or even each of the terminals in the network.

Drawing 500 of FIG. 5 illustrates one embodiment of transmitting beaconsignal bursts. A wireless terminal keeps on transmitting the beaconsignal bursts, e.g., beacon signal burst A 502, beacon signal burst B504, beacon signal burst C 506, etc., even if the wireless terminaldetermines that there is no other terminal in the vicinity or even ifthe terminal has already detected other terminals and may even haveestablished communication links with them.

The terminal transmits the beacon signal bursts in an intermittent(i.e., non-continuous) manner so that there are a number of symbolperiods between two successive beacon signal bursts. In general, thetime duration of a beacon signal burst is much shorter, e.g., in someembodiments at least 50 times shorter, than the number of symbol periodsin-between two successive beacon signal bursts, denoted as L 505. In oneembodiment, the value of L is fixed and constant, in which case thebeacon signal is periodic. In some embodiments the value of L is thesame and known for each of the terminals. In another embodiment, thevalue of L varies with time, e.g., according to a predetermined orpseudo-random pattern. For example, the number can be a number, e.g.,random number, distributed between constants L0 and L1.

Drawing 600 of FIG. 6 illustrates one exemplary embodiment in whichreceiving beacon signal bursts can occur during certain designated timeintervals, while at other times the receiver is off to conserve power.The wireless terminal listens to the spectrum of interest and attemptsto detect a beacon signal, which may be sent by a different terminal.The wireless terminal may continuously be in the listening mode for atime interval of a few symbol periods, which is called on time. The ontime 602 is followed by an off time 606 during which the wirelessterminal is in a power saving mode and does not receive any signal. Inthe off time, the wireless terminal, completely turns off the receivemodules. When the off time 606 ends, the terminal resumes to the on time604 and starts to detect a beacon signal again. The above procedurerepeats. Preferably, the length of an on time interval is shorter thanthat of an off time interval. In one embodiment, an on time interval maybe less than ⅕ of an off time interval. In one embodiment, the length ofeach of the on time intervals are the same, and the length of each ofthe off time intervals are also the same. In some embodiments the lengthof an off time interval depends on the latency requirement for a firstwireless terminal to detect the presence of another (second) wirelessterminal, if the second wireless terminal is actually present in thevicinity of the first wireless terminal. The length of an on timeinterval is determined so that the first wireless terminal has a greatprobability of detecting at least one beacon signal burst in the on timeinterval. In one embodiment, the length of the on time interval is afunction of at least one of the transmission duration of a beacon signalburst and the duration between successive beacon signal bursts. Forexample, the length of the on time interval is at least the sum of thetransmission duration of a beacon signal burst and the duration betweensuccessive beacon signal bursts.

Drawing 700 of FIG. 7 illustrates how a terminal detects the presence ofa second terminal when the two terminals use the beacon signaltransmission and reception procedure implemented.

The horizontal axis 701 represents time. The first wireless terminal 720arrives at the ad hoc network before the second wireless terminal 724shows up. The first wireless terminal 720, using transmitter 722, startsto transmit the beacon signal, which includes a sequence of beaconsignal bursts 710, 712, 714, etc. The second wireless terminal 724 showsup after the first wireless terminal 720 has already transmitted burst710. Suppose that the second wireless terminal 724, including receiver726, starts the on time interval 702. Note that the on time interval issufficiently large to cover the transmission duration of a beacon signalburst 712 and the duration between bursts 712 and 714. Therefore, thesecond wireless terminal 724 can detect the presence of beacon signalburst 712 in the on time interval 702, even though the first and thesecond wireless terminals (720, 724) do not have a common timingreference.

FIG. 8 illustrates one embodiment of an exemplary state diagram 800implemented in a wireless terminal.

When the wireless terminal is powered up, the wireless terminal entersthe state of 802, in which the terminal determines the start time of thenext beacon signal burst to be transmitted. In addition, the wirelessterminal determines the start time of the next on time interval for thereceiver. The wireless terminal may, and in some embodiments does, use atransmitter timer and a receiver timer to manage the start times. Thewireless terminal waits until either timer expires. Note that eithertimer may expire instantaneously, meaning that the wireless terminal isto transmit or detect a beacon signal burst upon power up.

Upon the expiration of the TX timer, the terminal enters the state of804. The wireless terminal determines the signal form of the burstincluding the frequency tone to be used by the burst, and transmits thebeacon signal burst. Once the transmission is done, the terminal returnsto the state of 802.

Upon the expiration of the RX timer, the wireless terminal enters thestate of 806. The wireless terminal is in the listening mode andsearches for a beacon signal burst. If the wireless terminal has notfound a beacon signal burst when the on time interval ends, then thewireless terminal returns to the state of 802. If the wireless terminaldetects a beacon signal burst of a new wireless terminal, the wirelessterminal may proceed to the state of 808 if the wireless terminalintends to communicate with the new terminal. In the state of 808, thewireless terminal derives the timing and/or frequency of the newwireless terminal from the detected beacon signal, and then synchronizesits own timing and/or frequency to the new wireless terminal. Forexample, the wireless terminal can use the beacon location in timeand/or in frequency as a basis for estimating the timing phase and/orfrequency of the new wireless terminal. This information can be used tosynchronize the two wireless terminals.

Once the synchronization is done, the wireless terminal may send (810)additional signal to the new terminal and establish a communicationlink. The wireless terminal and the new wireless terminal may then setup a peer-to-peer communication session. When the wireless terminal hasestablished a communication link with another terminal, the terminalshould keep on intermittently transmitting the beacon signal so thatother terminals, e.g., new wireless terminals can detect the wirelessterminal. In addition, the wireless terminal, keeps on periodicallyentering the on time intervals to detect new wireless terminals.

FIG. 9 provides a detailed illustration of an exemplary wirelessterminal 900, e.g., portable mobile node, implemented. The exemplarywireless terminal 900, depicted in FIG. 9, is a detailed representationof an apparatus that may be used as any one of terminals 102 and 104depicted in FIG. 1. In the FIG. 9 embodiment, the terminal 900 includesa processor 904, a wireless communication interface module 930, a userinput/output interface 940 and memory 910 coupled together by bus 906.Accordingly, via bus 906 the various components of the terminal 900 canexchange information, signals and data. The components 904, 906, 910,930, 940 of the terminal 900 are located inside a housing 902.

The wireless communication interface module 930 provides a mechanism bywhich the internal components of the wireless terminal 900 can send andreceive signals to/from external devices and another wireless terminal.The wireless communication interface module 930 includes, e.g., areceiver module 932 and a transmitter module 934, which are connectedwith a duplexer 938 with an antenna 936 used for coupling the wirelessterminal 900 to other terminals, e.g., via wireless communicationschannels.

The exemplary wireless terminal 900 also includes a user input device942, e.g., keypad, and a user output device 944, e.g., display, whichare coupled to bus 906 via the user input/output interface 940. Thus,user input/output devices 942, 944 can exchange information, signals anddata with other components of the terminal 900 via user input/outputinterface 940 and bus 906. The user input/output interface 940 andassociated devices 942, 944 provide a mechanism by which a user canoperate the wireless terminal 900 to accomplish various tasks. Inparticular, the user input device 942 and user output device 944 providethe functionality that allows a user to control the wireless terminal900 and applications, e.g., modules, programs, routines and/orfunctions, that execute in the memory 910 of the wireless terminal 900.

The processor 904 under control of various modules, e.g., routines,included in memory 910 controls operation of the wireless terminal 900to perform various signaling and processing. The modules included inmemory 910 are executed on startup or as called by other modules.Modules may exchange data, information, and signals when executed.Modules may also share data and information when executed. In the FIG. 9embodiment, the memory 910 of exemplary wireless terminal 900 includes asignaling/control module 912 and signaling/control data 914.

The signaling/control module 912 controls processing relating toreceiving and sending signals, e.g., messages, for management of stateinformation storage, retrieval, and processing. Signaling/control data914 includes state information, e.g., parameters, status and/or otherinformation relating to operation of the terminal. In particular, thesignaling/control data 914 includes beacon signal configurationinformation 916, e.g., the symbol periods in which the beacon signalbursts are to be transmitted and the signal forms of the beacon signalbursts including the frequency tones to be used, and receiver on timeand off time configuration information 918, e.g., the starting andending times of the on time intervals. The module 912 may access and/ormodify the data 914, e.g., update the configuration information 916 and918. The module 912 also includes the module for generating andtransmitting beacon signal bursts 911, the module for detecting beaconsignal bursts 913, and the synchronization module 915 for determiningand/or implementing timing and/or frequency synchronization informationas a function of received beacon signal information.

FIG. 10 is a drawing of a flowchart 1000 of an exemplary method ofoperating a portable wireless terminal. Operation of the exemplarymethod starts in step 1002, where the wireless terminal is powered onand initialized and proceeds to step 1004. In step 1004, the wirelessterminal is operated to transmit, during a first time interval, a beaconsignal and user data. Step 1004 includes sub-step 1006 and sub-step1008.

In sub-step 1006, the wireless terminal is operated to transmit a beaconsignal including a sequence of beacon signal bursts, each beacon signalburst including one or more beacon symbols, each beacon symbol occupyinga beacon symbol transmission unit, one or more beacon symbols beingtransmitted during each beacon symbol burst. In various embodiments, thetransmission power used for transmitting the beacon signal is from abattery power source. The number of beacon symbols in a beacon signalburst occupy less than 10 percent of the available beacon symboltransmission units. Each of the beacon signal bursts transmitted in thesequence of beacon signal bursts have the same period. In otherembodiments, at least some of the beacon signal bursts transmitted inthe sequence of beacon signal bursts have periods of different length.

Sub-step 1006 includes sub-step 1010. In sub-step 1010, the wirelessterminal is operated to transmit said beacon signal bursts at intervals,wherein a time period between two adjacent beacon signal bursts in saidsequence of beacon signal bursts is at least 5 times the duration ofeither of the two adjacent beacon signal bursts. The time spacingbetween beacon signal bursts occurring during the first period of timeis constant with the beacon signal bursts occurring in a periodic mannerduring the first period of time. In some such embodiments, the durationof beacon signal bursts during said first period of time is constant.The time spacing between beacon signal bursts occurring during the firstperiod of time varies with the beacon signal bursts occurring during thefirst period of time in accordance with a predetermined pattern. In somesuch embodiments, the duration of beacon signal bursts during said firstperiod of time is constant, the predetermined pattern varies dependingon the wireless terminal performing the transmitting step. In variousembodiments, the predetermined pattern is the same for all wirelessterminals in the system. The pattern is a pseudo random pattern.

In sub-step 1008, the wireless terminal is operated to transmit userdata during the first time interval, said user data being transmittedusing data symbols transmitted at an average per symbol power level thatis at least 50 percent lower than the average per beacon symbol powerlevel of beacon symbols transmitted during the first time interval. Theaverage per symbol transmission power level of each beacon symbol is atleast 10 dB higher than the average per symbol transmission power levelof symbols used to transmit data during the first time period. Theaverage per symbol transmission power level of each beacon symbol is atleast 16 dB higher than the average per symbol transmission power levelof symbols used to transmit data during the first time period.

In various embodiments, the beacon symbols are transmitted using OFDMtone-symbols, said beacon symbols occupying less than 1 percent of thetone-symbols of a transmission resource used by said wireless terminalduring a period of time including multiple beacon symbol bursts. In somesuch embodiments, the beacon symbols occupy less than 0.1 percent of thetone-symbols in a portion of said period of time including one beaconsignal burst and one interval between successive beacon signal bursts.

In sub-step 1008, the wireless terminal is operated to transmit userdata on at least 10 percent of the tone-symbols of the transmissionresource used by said wireless terminal during said first period oftime. In some such embodiments, the time duration of a beacon signalburst time period occurring in said first period of time is at least 50times shorter than a time period occurring between two consecutivebeacon signal bursts during said first period of time.

The portable wireless terminal includes an OFDM transmitter whichtransmits said beacon signal and the beacon signal is communicated usinga resource which is a combination of frequency and time. The portablewireless terminal includes a CDMA transmitter which transmits saidbeacon signal and the beacon signal is communicated using a resourcewhich is a combination of code and time.

FIG. 11 is a drawing of a flowchart 1100 of an exemplary method ofoperating a portable wireless terminal, e.g., a battery powered mobilenode. Operation starts in step 1102, where the portable wirelessterminal is powered on and initialized. Operation proceeds from startstep 1102 to step 1104, where the portable wireless terminal is operatedto transmit a beacon signal including a sequence of beacon signalbursts, each beacon symbol burst including one or more beacon symbols,each beacon symbol occupying a beacon symbol transmission unit, one ormore beacon symbols being transmitted during each burst. In some suchembodiments, the beacon symbols are transmitted using OFDM tone-symbols,and the beacon symbols occupy less than 1 percent of the tone-symbols ofa transmission resource used by said wireless terminal during a periodof time including multiple signal bursts. Operation proceeds from step1104 to step 1106.

In step 1106, the portable wireless terminal is operated to transmituser data on at least 10 percent of the tone-symbols used by saidwireless terminal during a period of time including multiple signalbursts. In some such embodiments, the time duration of a beacon signalburst occurring in said period of time is at least 50 times shorter thana time period occurring between two consecutive beacon signal burstsduring said period of time.

FIG. 12 is a drawing of a flowchart 1200 of an exemplary method ofoperating a portable wireless terminal, e.g., a battery powered mobilenode. Operation starts in step 1201, where the wireless terminal ispowered on and initialized. Operation proceeds from start step 1201 tostep 1202, where the wireless terminal checks as to whether the wirelessterminal is to transmit beacon signals. If it is determined in step 1202that the wireless terminal is to transmit beacon signals, e.g., thewireless terminal is in a mode of operation or state of operation inwhich the wireless terminal is to transmit beacon signals, operationproceeds from step 1202 to step 1204; otherwise operation proceeds backto the input of step 1202 for another check as to whether a beaconsignal is to be transmitted.

In step 1204, the wireless terminal checks whether or not it is time totransmit a beacon signal burst. If it is determined in step 1204 that itis time to transmit a beacon signal burst, then operation proceeds tostep 1206, where the wireless terminal transmits a beacon signal burstincluding one or more beacon symbols, each beacon symbol occupying abeacon symbol transmission unit. Operation proceeds from step 1206 tostep 1202.

If it is determined in step 1204 that it is not time to transmit abeacon signal burst, then operation proceeds to step 1208, in which thewireless terminal determines whether or not it is time for potentialuser data transmission. If it is determined in step 1208 that it is thetime allocated for potential user data transmissions, then operationproceeds from step 1208 to step 1210, otherwise operation proceeds fromstep 1208 to step 1202.

In step 1210, the wireless terminal determines if the wireless terminalis to transmit user data. If the wireless terminal is to transmit userdata, then operation proceeds from step 1210 to step 1212, where thewireless terminal transmits user data using data symbols transmitted atan average per symbol power level that is at least 50 percent lower thanthe average per beacon symbol power level of beacon symbols transmittedby said wireless terminal. If it is determined in step 1210, that thewireless terminal is not to transmit user data at this time, e.g., thewireless terminal has no backlog of user data waiting to be transmittedand/or a peer node to which the wireless terminal wants to send the datais not ready to receive the user data, then operation proceeds back tostep 1202.

FIG. 13 is a drawing of a flowchart 1300 of an exemplary method ofoperating a portable wireless terminal, e.g., a battery powered mobilenode. Operation starts in step 1302, where the wireless terminal ispowered on and initialized. Operation proceeds from start step 1302 tosteps 1304, 1306, 1308, connecting node A 1310 and connecting node B1312.

In step 1304, which is performed on an ongoing basis, the wirelessterminal tracks timing, outputting current time information 1314.Current time information 1314 identifies, e.g., an index value in arecurring timing structure being used by the wireless terminal.

In step 1306, the wireless terminal determines whether or not thewireless terminal is to transmit a beacon signal. The wireless terminaluses mode and/or state information 1316 and/or priority information 1318in determining whether or not the wireless terminal should transmit abeacon signal. If the wireless terminal decides in step 1306 that thewireless terminal is to transmit a beacon signal, operation proceeds tostep 1320, where the wireless terminal sets beacon active flag 1324.However, if the wireless terminal decides in step 1306 that the wirelessterminal is not to transmit a beacon signal, operation proceeds to step1322, where the wireless terminal clears the beacon active flag 1324.Operation proceeds from step 1320 or step 1322 back to step 1306, wherethe wireless terminal again tests as to whether or not a beacon signalshould be transmitted.

In step 1308, the wireless terminal determines whether or not thewireless terminal is cleared for data transmissions. The wirelessterminal uses mode and/or state information 1326, priority information1328, and/or peer node information 1330, e.g., information indicatingwhether or not a peer wireless terminal is receptive and able to receiveuser data, in determining whether or not the wireless terminal iscleared for data transmission. If the wireless terminal decides in step1308 that the wireless terminal is cleared to transmit user data,operation proceeds to step 1332, where the wireless terminal sets datatransmission flag 1336. However, if the wireless terminal decides instep 1308 that the wireless terminal is not cleared for user datatransmissions, operation proceeds to step 1334, where the wirelessterminal clears the data transmission flag 1336. Operation proceeds fromstep 1332 or step 1334 back to step 1308, where the wireless terminalagain tests as to whether or not the wireless terminal is cleared fordata transmission.

Returning to connecting node A 1310, operation proceeds from connectingnode A 1310 to step 1338. In step 1338, the wireless terminal checks asto whether the current time information 1314 indicates a beacon burstinterval with respect to the time structure information 1340 and whetheror not the beacon active flag 1324 is set. If the time indicates that itis a beacon burst interval and that the beacon active flag is set, thenoperation proceeds from step 1338 to step 1342; otherwise operationproceeds back to the input of step 1338 for another test of conditions.

In step 1342, the wireless terminal generates a beacon signal burst,said beacon signal burst including one or more beacon symbols, eachbeacon symbol occupying a beacon symbol transmission unit. The wirelessterminal utilizes current time information 1314 and stored beacon signaldefinition information 1344 in generating the beacon signal burst. Thebeacon signal definition information 1344 includes, e.g., burst signaldefinition information and/or pattern information. Beacon signal burstinformation includes information identifying a subset of OFDMtone-symbols used for conveying beacon symbols corresponding to thegenerated beacon burst signal for the wireless terminal within a set ofpotential OFDM tone-symbols which may be used to carry beacon symbols.The tone-subset for one beacon signal burst may be, and sometimes is,different from one beacon signal burst to the next within the samebeacon signal, e.g., in accordance with a predetermined hopping pattern.Beacon signal information includes information identifying themodulation symbol values to be conveyed by the beacon tone symbols ofthe generated beacon burst signal. A sequence of beacon signal bursts isused to define a beacon signal, e.g., corresponding to a particularwireless terminal. A pattern of beacon symbols is utilized to define thebeacon signal, e.g., a particular pattern within the beacon burstsignal.

Operation proceeds from step 1342 to step 1346, in which the wirelessterminal transmits the generated beacon burst signal. The wirelessterminal uses stored beacon symbol power level information 1348 todetermine the transmission power level of the beacon symbols within thetransmitted beacon burst signal. Operation then proceeds from step 1346to step 1338.

Returning to connecting node B 1312, operation proceeds from connectingnode B 1312 to step 1350. In step 1350, the wireless terminal checks asto whether the current time information 1314 indicates a datatransmission interval with respect to the time structure information1340, whether or not the data transmission flag 1336 is set, and whetherthe wireless terminal has data to transmit as indicated by user backloginformation 1352. If the indications are that it is a data transmissioninterval, that the data transmission flag 1336 is set and that thewireless terminal has data waiting to be transmitted, then operationproceeds from step 1350 to step 1354; otherwise operation proceeds backto the input of step 1350 for another test of conditions.

In step 1354, the wireless terminal generates signals including userdata 1356. User data 1356 includes, e.g., audio, image, file, and/ortext data/information intended for a peer of the wireless terminal.

Operation proceeds from step 1354 to step 1358, in which the wirelessterminal transmits the generated signals including user data. Thewireless terminal uses stored user data symbol power level information1360 to determine the transmission power level of the user data symbolsto be transmitted. Operation proceeds from step 1358 to step 1350 wherethe wireless terminal performs checks pertaining to user datatransmission.

The number of beacon symbols within a beacon signal burst occupy lessthan 10 percent of the available beacon symbol transmission units. Invarious embodiments, the user data symbols are transmitted at an averageper symbol power level that is at least 50 percent lower than theaverage per beacon symbol power level of transmitted beacon symbols.

FIG. 14 includes drawing 1400 illustrating exemplary beacon signalingfrom a portable wireless terminal, in accordance with an exemplaryembodiment in which the same beacon burst signal, beacon burst 1, isrepeated between non-beacon burst intervals. Each beacon signal burstincludes one or more beacon symbols, each beacon symbol occupying abeacon symbol transmission unit, one or more beacon symbols beingtransmitted during each beacon signal burst. Frequency, e.g., OFDMtones, is plotted on the vertical axis 1402, while time is plotted onhorizontal axis 1404. The following sequence is illustrated in drawing1400: beacon burst 1 signal interval including beacon burst 1 signal1406, non-burst interval 1408, beacon burst 1 signal interval includingbeacon burst 1 signal 1410, non-burst interval 1412, beacon burst 1signal interval including beacon burst 1 signal 1414, non-burst interval1416, beacon burst 1 signal interval including beacon burst 1 signal1418, non-burst interval 1420. In this example, each beacon burst signal(1406, 1410, 1414, 1418) corresponds to a beacon signal (1422, 1424,1426, 1428). In addition in this example, each beacon burst signal(1422, 1424, 1426, 1428) is the same; each beacon burst signal includesthe same beacon symbols.

FIG. 14 also includes drawing 1450 illustrating exemplary beaconsignaling from a portable wireless terminal in which a beacon signal isa composite signal including a sequence of beacon burst signals. Eachbeacon signal burst includes one or more beacon symbols, each beaconsymbol occupying a beacon symbol transmission unit, one or more beaconsymbols being transmitted during each beacon signal burst. Frequency,e.g., OFDM tones, is plotted on the vertical axis 1452, while time isplotted on horizontal axis 1454. The following sequence is illustratedin drawing 1450: beacon burst 1 signal interval including beacon burst 1signal 1456, non-burst interval 1458, beacon burst 2 signal intervalincluding beacon burst 2 signal 1460, non-burst interval 1462, beaconburst 3 signal interval including beacon burst 3 signal 1464, non-burstinterval 1466, beacon burst 1 signal interval including beacon burst 1signal 1468, non-burst interval 1470. In this example, beacon signal1472 is a composite signal including beacon burst 1 signal 1456, beaconburst 2 signal 1460 and beacon burst 3 signal 1464. In addition in thisexample, each beacon burst signal (beacon burst 1 signal 1456, beaconburst 2 signal 1460, beacon burst 3 signal 1464) is different; e.g.,each beacon burst signal includes a set of beacon symbols which does notmatch either set corresponding to the other two beacon burst signals.

The beacon symbols occupy less than 0.3 percent of the air resourceincluding one beacon signal burst and one interval between successivebeacon signal bursts. In some such embodiments, the beacon symbolsoccupy less than 0.1 percent of the air resource including one beaconsignal burst and one interval between successive beacon signal bursts.The air resource in some embodiments includes a set of OFDM tone-symbolscorresponding to a set of tones for a predetermined time interval.

FIG. 15 illustrates that different wireless terminals, transmitdifferent beacon signals including different beacon burst signals.Different beacon signals transmitted from wireless terminals can be, andsometimes are, used for wireless terminal identification. For example,consider that drawing 1500 includes a representation of a beacon burstsignal associated with wireless terminal A (“WT A”), while drawing 1550includes a representation of a beacon burst signal associated withwireless terminal B (“WT B”). Legend 1502 corresponds to drawing 1500,while legend 1552 corresponds to drawing 1550.

Legend 1502 indicates that with respect to the beacon burst signal forWT A, grid box 1510 represents a beacon symbol transmission unit, whilelarge letter B 1512 represents a beacon symbol conveyed by a beacontransmission unit. In drawing 1500, vertical axis 1504 representsfrequency, e.g., OFDM tone index, while horizontal axis 1506 representsbeacon transmission unit time index within the beacon burst signal.Beacon burst signal 1508 includes 100 beacon symbol transmission units1510. Two of those beacon symbol transmission units carry a beaconsymbol B 1512. A first beacon symbol has frequency index=3 and timeindex=0; a second beacon symbol has frequency index=9 and time index=6.The other beacon symbol transmission units are left unused. Thus in thisexample 2% of the transmission resources of the beacon burst are used toconvey beacon symbols. In some embodiments beacon symbols occupy lessthan 10% of the transmission resources of the beacon burst.

Legend 1552 indicates that with respect to the beacon burst signal forWT B, grid box 1510 represents a beacon symbol transmission unit, whilelarge letter B 1512 represents a beacon symbol conveyed by a beacontransmission unit. In drawing 1550, vertical axis 1554 representsfrequency, e.g., OFDM tone index, while horizontal axis 1556 representsbeacon transmission unit time index within the beacon burst signal.Beacon burst signal 1558 includes 100 beacon symbol transmission units1510. Two of those beacon symbol transmission units carry a beaconsymbol B 1512. A first beacon symbol has frequency index=3 and timeindex=2; a second beacon symbol has frequency index=7 and time index=6.The other beacon symbol transmission units are left unused. Thus in thisexample 2% of the transmission resources of the beacon burst are used toconvey beacon symbols.

FIG. 16 is a drawing 1600 and corresponding legend 1602 illustrating afeature of some embodiments, in which a beacon symbol transmission unitincludes a plurality of OFDM symbol transmission units. In this example,a beacon symbol transmission unit occupies two adjacent OFDM symboltransmission units. In other embodiments, a beacon symbol transmissionunit occupies a different number of OFDM transmission units, e.g., 3, or4. This feature of using multiple OFDM transmission units for a beaconsymbol transmission unit can facilitate easy detection of a beaconsignal, e.g., where precise timing and/or frequency synchronizationbetween wireless terminals may not exist. The beacon symbol includes aninitial beacon symbol portion followed by an extension beacon symbolportion. For example, the initial beacon symbol portion includes acyclic prefix portion followed by a body portion, and the extensionbeacon symbol portion is a continuation of the body portion.

Legend 1602 illustrates that for the exemplary beacon burst signal 1610,an OFDM transmission unit is represented by square box 1612, while abeacon symbol transmission unit is represented by rectangular box 1614with heavy borders. Large letters BS 1616 represent a beacon symbolconveyed by a beacon transmission unit.

In drawing 1600, vertical axis 1604 represents frequency, e.g., OFDMtone index, while horizontal axis 1606 represents beacon transmissionunit time index within the beacon burst signal, and horizontal axis 1608represents OFDM symbol time interval index within the beacon burstsignal. Beacon burst signal 1610 includes 100 OFDM symbol transmissionunits 1612 and 50 beacon symbol transmission units 1614. Two of thosebeacon symbol transmission units carry a beacon symbol BS 1616. A firstbeacon symbol has frequency index=3, beacon transmission unit timeindex=0, and OFDM time index 0-1; a second beacon symbol has frequencyindex=9, beacon transmission unit time index=3, and OFDM time index 6-7.The other beacon symbol transmission units are left unused. Thus in thisexample 4% of the transmission resources of the beacon burst are used toconvey beacon symbols. In some embodiments beacon symbols occupy lessthan 10% of the transmission resources of the beacon burst.

FIG. 17 is a drawing 1700 used to illustrate an exemplary beacon signalcomprising a sequence of beacon burst signals and to illustrate timingrelationships of some embodiments. Drawing 1700 includes a vertical axis1702 representing frequency, e.g., OFDM tone index, while the horizontalaxis 1704 represents time. The exemplary beacon signal of drawing 1700includes beacon burst 1 signal 1706, beacon burst 2 signal 1708 andbeacon burst 3 signal 1710. The exemplary beacon signal of drawing 1700is, e.g., the composite beacon signal 1472 of drawing 1450 of FIG. 14.

Beacon burst signal 1706 includes two beacon symbols 1707; beacon burstsignal 1708 includes two beacon symbols 1709; beacon burst signal 1710includes two beacon symbols 1711. In this example, the beacon symbols ineach burst occur in different beacon transmission unit positions in thetime/frequency grid. In addition in this example, the change ofpositions is in accordance with a predetermined tone hopping sequence.

Along time axis 1704, there is a beacon burst 1 signal time interval TB11712 corresponding to beacon burst 1 signal 1706, followed by a betweenburst time interval TBB1/2 1718, followed by a beacon burst 2 signaltime interval TB2 1714 corresponding to beacon burst 2 signal 1708,followed by a between burst time interval TBB2/3 1720, followed by abeacon burst 3 signal time interval TB3 1716 corresponding to beaconburst 3 signal 1710. In this example, the time between beacon bursts isat least 5 times greater than the time of an adjacent burst. Forexample, TBB1/2>5 TB1 and TBB1/2>5 TB2; TBB2/3>5 TB2 and TBB2/3>5 TB3.In this example, each of the beacon bursts (1706, 1708, 1710) have thesame time duration, e.g., TB1=TB2=TB3.

FIG. 18 is a drawing 1800 used to illustrate an exemplary beacon signalcomprising a sequence of beacon burst signals and to illustrate timingrelationships of some embodiments. Drawing 1800 includes a vertical axis1802 representing frequency, e.g., OFDM tone index, while the horizontalaxis 1804 represents time. The exemplary beacon signal of drawing 1800includes beacon burst 1 signal 1806, beacon burst 2 signal 1808 andbeacon burst 3 signal 1810. The exemplary beacon signal of drawing 1800is, e.g., the composite beacon signal 1472 of drawing 1450 of FIG. 14.

Beacon burst signal 1806 includes two beacon symbols 1807; beacon burstsignal 1808 includes two beacon symbols 1809; beacon burst signal 1810includes two beacon symbols 1811. In this example, the beacon symbols ineach burst occur in different beacon transmission unit positions in thetime/frequency grid. In addition in this example, the change ofpositions is in accordance with a predetermined tone hopping sequence.

Along time axis 1804, there is a beacon burst 1 signal time interval TB11812 corresponding to beacon burst 1 signal 1806, followed by a betweenburst time interval TBB1/2 1818, followed by a beacon burst 2 signaltime interval TB2 1814 corresponding to beacon burst 2 signal 1808,followed by a between burst time interval TBB2/3 1820, followed by abeacon burst 3 signal time interval TB3 1816 corresponding to beaconburst 3 signal 1810. In this example, the time between beacon bursts isat least 5 times greater than the time of an adjacent burst. Forexample, TBB1/2>5 TB1 and TBB1/2>5 TB2; TBB2/3>5 TB2 and TBB2/3>5 TB3.In this example, each of the beacon bursts (1806, 1808, 1810) have thedifferent time duration, e.g., TB1≠TB2≠TB3≠TB1. At least two of thebeacon burst signals in the composite beacon signal have differentduration.

FIG. 19 is a drawing 1900 illustrating exemplary air link resourcepartitioning by a wireless terminal in a mode of operation in which thewireless terminal transmits a beacon signal. Vertical axis 1902represents frequency, e.g., OFD tones, while horizontal axis 1904represents time. In this example, there is a beacon transmissionresource 1906, followed by an other use resource 1908, followed by abeacon transmission resource 1906′, followed by an other use resource1908′, followed by a beacon transmission resource 1906″, followed by another use resource 1908″, followed by a beacon transmission resource1906′″, followed by an other use resource 1908′″. A beacon transmissionresource of FIG. 19 corresponds, e.g., to a beacon burst of FIG. 14,while an other use resource of FIG. 19 corresponds, e.g., to a non-burstinterval of FIG. 14.

FIG. 20 depicts an exemplary other use resource, e.g., resource 2000,for an exemplary mode of wireless terminal operation in which thewireless terminal transmits a beacon signal and can receive and/ortransmit user data, e.g., an active mode of operation. Other useresource 2000 occurs during non-burst interval 2002 and includes: abeacon monitoring resource 2004, a user data transmission/receiveresource 2006 and a silence or unused resource 2008. The beaconmonitoring resource 2004 represents air link resources, e.g., acombination of frequency and time, in which the wireless terminaldetects for the presence of other beacon signals, e.g., from otherwireless terminals and/or fixed position reference beacon signaltransmitters. The user data resource 2006 represents air link resources,e.g., a combination of frequency and time, in which the wirelessterminal can transmit user data and/or receive user data. The silenceair link resource 2008 represents unused air link resources, e.g., wherethe wireless terminal neither receives nor transmits. During the silenceresource 2008, the wireless can be, and sometimes is, in a sleep statein which power consumption is lowered to conserve energy.

FIG. 21 illustrates two exemplary modes of wireless terminal operationin which the wireless terminal is transmitting a beacon signal, e.g., aninactive mode and an active mode. Drawing 2100 corresponds to theexemplary inactive mode of operation, while drawing 2150 corresponds tothe active mode of operation.

In the exemplary inactive mode of operation, the wireless terminal doesnot transmit or receiver user data. In drawing 2100, the air linkresource used by the wireless terminal occupies N tones 2108. In oneembodiment, N is greater than or equal to 100. In drawing 2100, there isa beacon transmission burst resource 2102 with a corresponding timeduration T1inactive 2110, followed by a monitor and receive beaconinformation resource 2104 with a corresponding time duration T2inactive2112, followed by a silence resource 2106 with a corresponding timeduration T3inactive 2114. In various embodiments,T1inactive<T2inactive<T3inactive, T2inactive>4T1inactive,T3inactive>10T2inactive. For, example, in one exemplary embodimentN>100, e.g. 113, T1inactive=50 OFDM symbol transmission time intervals,T2inactive=200 OFDM symbol transmission time intervals, andT3inactive=2000 OFDM symbol transmission time intervals. In such anembodiment, if beacon symbols are allowed to occupy at most 10% of theburst beacon signal resource, beacon symbols occupy approximately atmost 0.22% of the total resource.

In the exemplary active mode of operation, the wireless terminal cantransmit and receive user data. In drawing 2150, the air link resourceused by the wireless terminal occupies N tones 2108. In one embodiment,N is greater than or equal to 100. In drawing 2150, there is a beacontransmission burst resource 2152 with a corresponding time durationT1active 2162, followed by a monitor and receive beacon informationresource 2154 with a corresponding time duration T2active 2164, followedby a user data transmit/receive resource 2156 with a corresponding timeduration T3active 2166, followed by a silence resource 2158 with acorresponding time duration T4active 2168. In various embodiments,T1active<T2active<T3active, T2active>4T1active,(T3active+T4active)>10T2inactive. In various embodimentsT1inactive=T1active. There are guard intervals between at least some ofthe different types of intervals.

FIG. 22 is a drawing 2200 and corresponding legend 2202 illustratingexemplary wireless terminal air link resource utilization during anexemplary first time interval 2209 including two beacon bursts. Legend2202 indicates that a square 2204 indicates an OFDM tone-symbol, thebasic transmission unit of the air link resource. Legend 2202 alsoindicates that: (i) a beacon symbol is indicated by a shaded square 2206and is transmitted at an average transmission power level PB, (ii) auser data symbol is indicated by a letter D 2208 and that data symbolsare transmitted such as to have an average transmission power level PD,and (iii) PB>2PD.

In this example, the beacon transmission resource 2210 includes 20 OFDMtone-symbols; the beacon monitoring resource 2212 includes 40 OFDMtone-symbols; the user data transmission/receive resource 2214 includes100 OFDM tone-symbols; and the beacon transmission resource 2216includes 20 OFDM tone-symbols.

Beacon transmission resources 2210 and 2216 each carry one beacon symbol2206. This represents 5% of the transmission resources allocated forbeacon burst signaling. Forty-eight (48) of the 100 OFDM symbols of theuser data TX/RX resource 2214 carry a user data symbol being transmittedby the wireless terminal. This represents 48/180 OFDM symbols being usedby the wireless terminal during the first time interval 2209. Assumethat the WT switches from TX to receive for the 6th OFDM symboltransmission time interval of the user data portion, then user datasymbols are transmitted on 48/90 OFDM tone-symbols used by the wirelessterminal for transmission during the first time interval. When thewireless terminal transmits user data, the wireless terminal transmitsuser data on at least 10% of the transmission resource used by thewireless terminal during a period of time including multiple beaconsignal bursts.

At different times the user data transmit/receive resource can be, andsometime is used differently, e.g., exclusively for transmissionincluding user data, exclusively for reception including user data,portioned between receive and transmit, e.g., on a time share basis.

FIG. 23 is a drawing 2300 and corresponding legend 2302 illustratingexemplary wireless terminal air link resource utilization during anexemplary first time interval 2315 including two beacon bursts. Legend2302 indicates that a square 2304 indicates an OFDM tone-symbol, thebasic transmission unit of the air link resource. Legend 2302 alsoindicates that: (i) a beacon symbol is indicated by a large verticalarrow 2306 and is transmitted at an average transmission power level PB,(ii) user data symbols are indicated by small arrows 2308, 2310, 2312,2314, which correspond to different phases (θ1, θ2, θ3, θ4),respectively, e.g., corresponding to QPSK, and that data symbols aretransmitted such as to have an average transmission power level PD, and(iii) PB>2PD.

In this example, the beacon transmission resource 2316 includes 20 OFDMtone-symbols; the beacon monitoring resource 2318 includes 40 OFDMtone-symbols; the user data transmission/receive resource 2320 includes100 OFDM tone-symbols; and the beacon transmission resource 2322includes 20 OFDM tone-symbols.

Beacon transmission resources 2316 and 2322 each carry one beacon symbol2306. In this embodiment, the beacon symbols have the same amplitude andphase. This amount of beacon symbols represents 5% of the transmissionresources allocated for beacon burst signaling. Forty-eight (48) of the100 OFDM symbols of the user data TX/RX resource 2320 carry a user datasymbol. In this embodiment, different data symbols can and sometimes do,have different phase. Different data symbols can, and sometimes do havedifferent amplitude. This amount of data symbols represents 48/180 OFDMsymbols being used by the wireless terminal during the first timeinterval 2315. Assume that the WT switches from TX to receive for the6th OFDM symbol transmission time interval of the user data portion,then user data symbols are transmitted on 48/90 OFDM tone-symbols usedby the wireless terminal for transmission during the first timeinterval. When the wireless terminal transmits user data, the wirelessterminal transmits user data on at least 10% of the transmissionresource used by the wireless terminal during a period of time includingmultiple beacon signal bursts.

At different times the user data transmit/receive resource can be, andsometime is used differently, e.g., exclusively for transmissionincluding user data, exclusively for reception including user data,portioned between receive and transmit, e.g., on a time share basis.

FIG. 24 illustrates an alternative descriptive representation withrespect to beacon signals. Drawing 2400 and associated legend 2402 areused to depict an exemplary beacon signal. Vertical axis 2412 representsfrequency, e.g., OFDM tone index, while horizontal axis 2414 representsbeacon resource time index. Legend 2402 identifies that a beacon signalburst is identified by heavy line rectangle 2404, a beacon symboltransmission unit is identified by a square box 2406, and a beaconsymbol is represented by a bold letter B 2416. The beacon signalresource 2410 includes 100 beacon symbol transmission units 2406. Threebeacon burst signals 2404 are shown corresponding to time indexvalues=0, 4, and 8. One beacon symbol 2416 occurs in each beacon burstsignal, and the location of the beacon symbol changes from one burstsignal to the next within the beacon signal, e.g., in accordance with apredetermined pattern and/or equation. In this embodiment, the beaconsymbol location follows a slope. In this example, the beacon bursts areseparated from each other by three times the duration of a beacon burst.In various embodiments, the beacon bursts are separated from one anotherby at least twice the duration of a beacon symbol. A beacon burst mayoccupy two or more successive beacon resource time intervals, e.g., withthe same tone being used for multiple successive beacon time indexes. Abeacon burst includes multiple beacon symbols. In some such embodiments,beacon symbols occupy 10% or less of the beacon signal resource.

FIG. 25 is a drawing of an exemplary portable wireless terminal 2500,e.g., mobile node. Exemplary portable wireless terminal 2500 may be anyof the wireless terminals of FIG. 1.

Exemplary wireless terminal 2500 includes a receiver module 2502, atransmission module 2504, a duplex module 2503, a processor 2506, userI/O devices 2508, a power supply module 2510 and memory 2512 coupledtogether via a bus 2514 over which the various elements may interchangedata and information.

Receiver module 2502, e.g., an OFDM receiver, receives signals fromother wireless terminals and/or fixed location beacon transmitters,e.g., beacon signals and/or user data signals.

Transmission module 2504, e.g., an OFDM transmitter, transmits signalsto other wireless terminals, said transmitted signals including beaconsignals and user data signals. A beacon signal includes a sequence ofbeacon signal bursts, each beacon signal burst including one or morebeacon symbols, and each beacon symbol occupies a beacon symboltransmission unit. One or more beacon symbols are transmitted bytransmission module 2504 for each transmitted beacon signal burst.

In various embodiments, the transmission module 2504 is an OFDMtransmitter which transmits beacon signals and the beacon signal iscommunicated using a resource which is a combination of frequency andtime. In various other embodiments, the transmission module 2504 is aCDMA transmitter which transmits beacon signals and the beacon signal iscommunicated using a resource which is a combination of code and time.

Duplex module 2503 is controlled to switch the antenna 2505 between thereceiver module 2502 and transmission module 2504, as part of a timedivision duplex (TDD) spectrum system implementation. The duplex module2503 is coupled to antenna 2505 via which the wireless terminal 2500receives signals 2582 and transmits signals 2588. Duplex module 2503 iscoupled to receiver module 2502 via link 2501 over which receivedsignals 2584 are conveyed. Signal 2584 is, a filtered representation ofsignal 2582. Signal 2584 is, the same as signal 2582, e.g., module 2503functions as a pass thru device without filtering. Duplex module 2503 iscoupled to transmission module 2504 via link 2507 over which transmitsignals 2586 are conveyed. Signal 2588 is, a filtered representation ofsignal 2586. Signal 2588 is, the same signal 2586, e.g., duplex module2503 functions as a pass thru device without filtering.

User I/O devices 2508 include, e.g., microphone, keyboard, keypad,switches, camera, speaker, display, etc. User devices 2508, allow a userto input data/information, access output data/information, and controlat least some operations of the wireless terminal, e.g., initiate apower up sequence, attempt to establish a communications session,terminate a communications session.

The power supply module 2510 includes a battery 2511 utilized as asource of portable wireless terminal power. The output of the powersupply module 2510 is coupled to the various components (2502, 2503,2504, 2506, 2508, and 2512) via power bus 2509 to provide power. Thus,transmission module 2504 transmits beacon signals using battery power.

Memory 2512 includes routines 2516 and data/information 2518. Theprocessor 2506, e.g., a CPU, executes the routines 2516 and uses thedata/information 2518 in memory 2512 to control the operation of thewireless terminal 2500 and implement methods. Routines 2516 includebeacon signal generation module 2520, user data signal generation module2522, transmission power control module 2524, beacon signal transmissioncontrol module 2526, mode control module 2528 and duplex control module2530.

Beacon signal generation module 2520 uses the data information 2518 inmemory 2512 including stored beacon signal characteristic information2532 to generate beacon signals, a beacon signal including a sequence ofbeacon signal bursts, each beacon signal burst including one or morebeacon symbols.

User data signal generation module 2522 uses the data/information 2518including user data characteristic information 2534 and user data 2547to generate a user data signal, said user data signal including userdata symbols. For example, information bits representing the user data2547 are mapped to a set of data symbols, e.g., OFDM data modulationsymbols in accordance with constellation information 2564. Transmissionpower control module 2524 uses the data/information 2518 includingbeacon power information 2562 and user data power information 2566 tocontrol the transmission power level of beacon symbols and data symbols.During a first period of time, the transmission power control module2524 controls the data symbols to be transmitted at an average persymbol power level that is at least 50 percent lower than the averageper beacon symbol power level of the beacon symbols transmitted. Thetransmission power control module 2524 controls the average per symboltransmission power level of each beacon symbol transmitted during afirst period of time to be at least 10 dB higher than the average persymbol transmission power level of symbols used to transmit user dataduring a first period of time. The transmission power control module2524 controls the average per symbol transmission power level of eachbeacon symbol transmitted during a first period of time to be at least16 dB higher than the average per symbol transmission power level ofsymbols used to transmit user data during a first period of time. Thebeacon symbol power level and one or more data symbol power levels areinterrelated with respect to a reference being used by the wirelessterminal, and the reference may be, and sometimes does change. In somesuch embodiments, the first period of time is a time interval duringwhich the reference level does not change.

Beacon signal transmission control module 2526 uses the data/information2518 including the timing structure information 2536 to control thetransmission module 2504 to transmit beacon signal bursts at intervals.The time period between two adjacent beacon signal bursts in a sequenceof beacon signal bursts is controlled to be at least 5 times theduration of either of the two adjacent beacon signal bursts. In variousembodiments, at least some different beacon signal bursts have periodsof different lengths.

Mode control module 2528 controls the wireless terminal's mode ofoperation with the current mode of operation being identified by modeinformation 2540. The various modes of operation include an OFF mode, areceive only mode, an inactive mode, and an active mode. In the inactivemode, the wireless terminal can send and receive beacon signals but isnot permitted to transmit user data. In the active mode, the wirelesscan send and receive user data signals in addition to beacon signals. Ininactive mode, the wireless terminal is in a silence, e.g., sleep, stateof low power consumption, for a longer time than in an active mode ofoperation.

Duplex control module 2530 controls the duplex module 2503 to switch theantenna connection between receiver module 2502 and transmission module2504 in response to TDD system timing information and/or user needs. Forexample, a user data interval in a timing structure is, available foreither receive or transmit with the selection being a function of thewireless terminal needs. In various embodiments, the duplex controlmodule 2530 also operates to shut down at least some circuitry inreceiver module 2502 and/or transmission module 2504, when not in use toconserve power.

Data/information 2518 includes stored beacon signal characteristicinformation 2532, table 2533, user data characteristic information 2534,timing structure information 2536, air link resource information 2538,mode information 2540, generated beacon signal information 2542,generated data signal information 2544, duplex control signalinformation 2546, and user data 2547. Stored beacon signalcharacteristic information 2532 includes one or more sets of beaconburst information (beacon burst 1 information 2548, . . . , beacon burstN information 2550), beacon symbol information 2560, and powerinformation 2562. Table 2533 is a table mapping device identifiers tosets of time indices. Table 2533 maps a first device identifier to afirst set of time indices and a second device identifier to a second setof time indices.

Beacon burst 1 information 2548 includes information identifying beacontransmission units carrying a beacon symbol 2556 and beacon burstduration information 2558. Information identifying beacon transmissionunits carrying a beacon symbol 2556 is used by beacon signal generationmodule 2520 in identifying which beacon transmission units in a beaconsignal burst are to be occupied by beacon symbols. In variousembodiments, the other beacon transmission units of the beacon burst areset to be nulls, e.g., no transmission power applied with respect tothose other beacon transmission units. The number of beacon symbols in abeacon signal burst occupy less than 10 percent of the available beaconsymbol transmission units. The number of beacon symbols in a beaconsignal burst occupy less than or equal to 10 percent of the availablebeacon symbol transmission units. Beacon signal burst durationinformation 2558 includes information defining the duration of beaconburst 1. In some embodiments each of the beacon bursts have the sameduration, while in other embodiments, different beacon bursts within thesame composite beacon signal can, and sometimes do, have differentduration. One beacon burst in a sequence of beacon bursts has adifferent duration, and this may be useful for synchronization purposes.

Beacon symbol information 2560 includes information defining the beaconsymbol, e.g., the modulation value and/or characteristic of the beaconsymbol. In various embodiments, the same beacon symbol value is used foreach of the identified positions to carry a beacon symbol in information2556, e.g., the beacon symbol has the same amplitude and phase. Invarious embodiments, different beacon symbol values can be, andsometimes are used for at least some of the identified positions tocarry a beacon symbol in information 2556, e.g., the beacon symbol valuehas the same amplitude but can have one of two potential phases, thusfacilitating the communication of additional information via the beaconsignal. Power information 2562 includes, e.g., power gain scale factorinformation used with respect to beacon symbol transmissions.

User data characteristic information 2534 includes constellationinformation 2564 and power information 2566. Constellation information2564 identifies, e.g., QPSK, QAM 16, QAM 64, and/or QAM256, etc, andmodulation symbol values associated with the constellation. Powerinformation 2566 includes, e.g., power gain scale factor informationused with respect to data symbol transmissions.

Timing structure information 2536 includes information identifyingintervals associated with various operations, e.g., a beacontransmission time interval, an interval for monitoring for beaconsignals from other wireless terminals and/or fixed location beacontransmitters, a user data interval, a silence, e.g., sleep, interval,etc. Timing structure information 2536 includes transmission timingstructure information 2572 which includes beacon burst durationinformation 2574, beacon burst spacing information 2576, patterninformation 2578, and data signaling information 2580.

The beacon burst duration information 2574 identifies that the durationof a beacon burst is a constant, e.g., 100 successive OFDM transmissiontime intervals. The beacon burst duration information 2574 identifiesthat the duration of a beacon burst varies, e.g., in accordance with apredetermined pattern specified by pattern information 2578. In variousembodiments, the predetermined pattern is a function of a wirelessterminal identifier. In other embodiments, the predetermined pattern isthe same for all wireless terminals in the system. The predeterminedpattern is a pseudo random pattern.

Beacon burst duration information 2574 and beacon burst spacinginformation 2576 indicate that the duration of a beacon burst is atleast 50 times shorter than the interval of time from the end of thebeacon burst to the start of the next beacon burst. The beacon burstspacing information 2576 indicates that the spacing between beaconbursts is constant with beacon bursts occurring in a periodic mannerduring a period of time in which the wireless terminal is transmittingbeacon signals. The beacon burst spacing information 2576 indicates thatthe beacon bursts are transmitted with the same interval spacing whetherthe wireless terminal is in an inactive mode or an active mode. In otherembodiments, the beacon burst spacing information 2576 indicates thatthe beacon bursts are transmitted using different interval spacing as afunction of the wireless terminal operational mode, e.g., whether thewireless terminal is in an inactive mode or an active mode.

Air link resource information 2538 includes beacon transmission resourceinformation 2568 and other use resource information 2570. Air linkresources are defined in terms of OFDM tone-symbols in a frequency timegrid, e.g., as part of a wireless communication system such as a TDDsystem. Beacon transmission resource information 2568 includesinformation identifying air link resources allocated to WT 2500 forbeacon signals, e.g., a block of OFDM tone-symbols to be used totransmit a beacon burst including at least one beacon symbol. Beacontransmission resource information 2568 also includes informationidentifying beacon transmission units. In some embodiments a beacontransmission unit is a single OFDM tone-symbol. A beacon transmissionunit is a set of OFDM transmission units, e.g., a set of contiguous OFDMtone-symbols. Other use resource information 2570 includes informationidentifying air link resources to be used by WT 2500 for other purposessuch as, e.g., beacon signal monitoring, receive/transmit user data.Some of the air link resources may be, and sometimes are, intentionallynot used, e.g., corresponding to a silence state, e.g., sleep state,which conserves power. In some embodiments a beacon symbol istransmitted using the air link resource of OFDM tone-symbols, and beaconsymbols occupy less than 1 percent of the tone-symbols of thetransmission resource used by said wireless terminal during a period oftime including multiple beacon signal bursts and at least one user datasignal. In various embodiments, beacon signals occupy less than 0.3percent of the tone symbols in a portion of a period of time, saidportion of said period of time including one beacon signal burst and oneinterval between successive beacon signal bursts. In variousembodiments, beacon signals occupy less than 0.1 percent of the tonesymbols in a portion of a period of time, said portion of said period oftime including one beacon signal burst and one interval betweensuccessive beacon signal bursts. In various embodiments, during at leastsome modes of operation, e.g., an active mode of operation, thetransmission module 2504 can transmit user data, and when the wirelessterminal transmits user data, user data is transmitted on at least 10percent of the tone-symbols of the transmission resource used by saidwireless terminal during a period of time including the user data signaltransmission and two adjacent beacon signal bursts.

Generated beacon signal 2542 is an output of beacon signal generationmodule 2520, while generated data signal 2544 is an output of user datasignal generation module 2522. The generated signals (2542, 2544) aredirected to transmission module 2504. User data 2547 includes, e.g.,audio, voice, image, text and/or file data/information that is used asinput by user data signal generation module 2522. Duplex control signal2546 represents output of duplex control module 2530, and the outputsignal 2546 is directed to duplex module 2503 to control antennaswitching and/or to a receiver module 2502 or transmitter module 2504 toshut down at least some circuitry and conserve power.

FIG. 26 is a drawing of a flowchart 2600 of an exemplary method ofoperating a communications device, e.g., a battery powered wirelessterminal. Operation starts in step 2602, where the communications deviceis powered on and initialized. Operation proceeds from start step 2602to step 2604 and step 2606.

In step 2604, which is performed on an ongoing basis, the communicationsdevice maintains time information. Time information 2605 is output fromstep 2604 and used in step 2606. In step 2606, the communications devicedetermines whether a time period is a beacon receive time period, abeacon transmission time period, or a silence time period, and proceedsdifferently depending on the determination. If the time period is abeacon receive time period, then operation proceeds from step 2606 tostep 2610, where the communications device performs a beacon signaldetection operation.

If the time period is a beacon transmission time period, then operationproceeds from step 2606 to step 2620, where the communications devicetransmits at least a portion of a beacon signal, said transmittedportion including at least one beacon symbol.

If the time period is a silence time period, then operation proceedsfrom step 2606 to step 2622, where the communications device refrainsfrom transmitting and refrains from operating to detect beacon signals.The communications device goes into a silence, e.g., sleep, mode in step2622 and conserves battery power.

Returning to step 2610, operation proceeds from step 2610 to step 2612.In step 2612, the communications device determines if a beacon has beendetected. If a beacon has been detected, operation proceeds from step2612 to step 2614. However, if a beacon was not detected, operationproceeds from step 2612 via connecting node A 2613 to step 2606. In step2614, the communications device adjusts communications devicetransmission time based on a detected portion of a received signal.Adjustment information 2615, obtained from step 2614 is used inmaintaining time information for the communications device in step 2604.The timing adjustments adjusts the beacon signal transmission timeperiod to occur during a time period known to by used by the devicewhich transmitted the received beacon signal portion to receive beaconsignals. Operation proceeds from step 2614 to step 2616, where thecommunications device transmits a signal in accordance with the adjustedcommunications device transmission timing, e.g., a beacon signal. Then,in step 2618, the communications device establishes a communicationssession with the device from which the detected portion of a beaconsignal was received. Operation proceeds from any of steps 2618, 2620, or2622 via connecting node A 2613 to step 2606.

Step 2604 includes at least one of sub-step 2608 and 2609. In sub-step2608, the communications device pseudo randomly adjusts the start of atleast one of a beacon transmission time period and a beacon receive timeperiod in a recurring sequence of such time periods. For example, acommunication device at a particular time, e.g., following power on orentering a new region, may not be synchronized with respect to any othercommunication device, and may perform sub-step 2608 one or more times,in order to increase the probability of detecting a beacon signal fromanother communications device while having a limited beacon detectiontime interval in a recurring time structure. Thus sub-step 2608 caneffectively shift relative timing between two peers. In sub-step 2609,the communications device sets beacon receive and transmission timeperiods to occur on a periodic basis.

In various embodiments, the beacon receive time period is longer thanthe beacon transmission time period. The beacon receive and transmissiontime periods are non-overlapping, and the beacon receive time period isat least two times the beacon transmission time period. The silence timeperiod occurs between beacon receive and beacon transmission timeperiods. In various embodiments, the silence period is at least twiceone of the beacon transmission time periods and beacon receive timeperiods.

FIG. 27 is a drawing of an exemplary communications device which isportable wireless terminal 2700, e.g., mobile node. Exemplary portablewireless terminal 2700 may be any of the wireless terminals of FIG. 1.Exemplary wireless terminal 2700 is, e.g., a communication device whichis part of a time division duplex (TDD) orthogonal frequency divisionmultiplexing (OFDM) wireless communications system supporting peer-peerdirect communications between mobile nodes. Exemplary wireless terminal2700 can both transmit and receive beacon signals. Exemplary wirelessterminal 2700 performs timing adjustments based on detected beaconsignals, e.g., from a peer wireless terminal transmitting beacon signalsand/or from a fixed beacon transmitter, to establish timingsynchronization.

Exemplary wireless terminal 2700 includes a receiver module 2702, atransmission module 2704, a duplex module 2703, a processor 2706, userI/O devices 2708, a power supply module 2710 and memory 2712 coupledtogether via a bus 2714 over which the various elements may interchangedata and information.

Receiver module 2702, e.g., an OFDM receiver, receives signals fromother wireless terminals and/or fixed location beacon transmitters,e.g., beacon signals and/or user data signals.

Transmission module 2704, e.g., an OFDM transmitter, transmits signalsto other wireless terminals, said transmitted signals including beaconsignals and user data signals. A beacon signal includes a sequence ofbeacon signal bursts, each beacon signal burst including one or morebeacon symbols, and each beacon symbol occupies a beacon symboltransmission unit. One or more beacon symbols are transmitted bytransmission module 2704 for each transmitted beacon signal burst.Transmission module 2704 transmits during a beacon transmission timeperiod at least a portion of a beacon signal, e.g., a beacon burstsignal, said transmitted portion including at least one beacon symbol,e.g., a relatively high power tone with respect to the power level ofuser data symbols.

In various embodiments, the transmission module 2704 is an OFDMtransmitter which transmits beacon signals and the beacon signal iscommunicated using a resource which is a combination of frequency andtime. In various other embodiments, the transmission module 2704 is aCDMA transmitter which transmits beacon signals and the beacon signal iscommunicated using a resource which is a combination of code and time.

Duplex module 2703 is controlled to switch the antenna 2705 between thereceiver module 2702 and transmission module 2704, as part of a timedivision duplex (TDD) implementation. The duplex module 2703 is coupledto antenna 2705 via which the wireless terminal 2700 receives signals2778 and transmits signals 2780. Duplex module 2703 is coupled toreceiver module 2702 via link 2701 over which received signals 2782 areconveyed. Signal 2782 is, a filtered representation of signal 2778.Signal 2782 is the same as signal 2778, e.g., where duplex module 2703functions as a pass through device without filtering. Duplex module 2703is coupled to transmission module 2704 via link 2707 over which transmitsignals 2784 are conveyed. Signal 2780 is, a filtered representation ofsignal 2784. Signal 2780 is the same as signal 2784, e.g., where duplexmodule 2703 functions as a pass through device without filtering.

User I/O devices 2708 include, e.g., microphone, keyboard, keypad,switches, camera, speaker, display, etc. User devices 2708, allow a userto input data/information, access output data/information, and controlat least some operations of the wireless terminal, e.g., initiate apower up sequence, attempt to establish a communications session,terminate a communications session.

The power supply module 2710 includes a battery 2711 utilized as asource of portable wireless terminal power. The output of the powersupply module 2710 is coupled to the various components (2702, 2703,2704, 2706, 2708, and 2712 via power bus 2709 to provide power. Thus,transmission module 2704 transmits beacon signals using battery power.

Memory 2712 includes routines 2716 and data/information 2718. Theprocessor 2706, e.g., a CPU, executes the routines 2716 and uses thedata/information 2718 in memory 2712 to control the operation of thewireless terminal 2700 and implement methods. Routines 2716 includebeacon signal detection module 2720, a silence state control module2722, a transmission time adjustment module 2724, a transmission controlmodule 2726, a communication session initiation module 2728, a beacondetection control module 2730, a timing adjustment module 2732, a modecontrol module 2734, a beacon signal generation module 2736, a user datasignal generation module 2738, a user data recovery module 2740, and aduplex control module 2742.

Beacon signal detection module 2720 performs a beacon signal detectionoperation during a beacon receive time period to detect the receipt ofat least a portion of a beacon signal. In addition, the beacon signaldetection module 2720 sets the detected beacon flag 2750 indicating thereceipt of a beacon signal portion in response to a detected beaconsignal portion. Detected beacon signal portion 2754 is an output ofbeacon signal detection module 2720. In addition, the beacon signaldetection module 2720 sets the detected beacon flag 2750 indicating thereceipt of a beacon signal portion in response to a detected beaconsignal portion. The beacon signal detection module 2720 performsdetections as a function of energy level comparisons. The beacon signaldetection module 2720 performs detections as a function of detectedbeacon symbol pattern information, e.g., in a monitored air linkresource corresponding to a beacon burst. The beacon signal detectionmodule 2720, recovers information from the detected beacon signalportion, e.g., information identifying the source, e.g., wirelessterminal, which transmitted the beacon signal. For example, differentwireless terminals may, and sometimes do have different beacon burstpatterns and/or signatures.

Silence state control module 2722 controls wireless terminal operationduring a silence period, occurring, e.g., between beacon receive andbeacon transmission time periods, to neither transmit nor operate todetect beacon signals.

Transmission time adjustment module 2724 adjusts the communicationsdevice's transmission time based on a detected portion of a receivedbeacon signal. For example, consider that the communications system is,e.g., an ad hoc network, and the received beacon signal portion is fromanother wireless terminal. As another example, consider the systemincludes fixed location beacon transmitters serving as references, andthat the detected beacon signal portion is sourced from such atransmitter; the transmission time adjustment module 2724 adjusts thewireless terminal's transmission time to synchronize with respect to thereference. Alternatively, consider the system does not include fixedlocation beacon transmitters, or that the wireless terminal can notcurrently detect such a beacon signal, and that the detected beaconsignal portion is from another wireless terminal, then the transmissiontime adjustment module 2724 adjusts the wireless terminal's transmissiontime to synchronize with respect to the peer wireless terminal which hadtransmitted the beacon signal. Including both fixed location beacons andwireless terminal beacons, the fixed locations beacons are used, whenavailable, to achieve a coarse level of system synchronization, and thewireless terminal beacons are used to achieve a higher degree ofsynchronization between peers. Detected timing offset based on detectedbeacon signal portion 2756 is an output of transmission time adjustmentmodule 2724.

In various embodiments, the transmission time adjustment module 2724adjusts the beacon signal transmission time period to occur during atime period known to be used by the device, e.g., other wirelessterminal, which transmitted the received portion to receive beaconsignals. Thus the transmission time adjustment module 2724 sets WT2700's beacon to be transmitted such that it is expected to hit the timewindow in which the peer is attempting to detect beacons.

Transmission control module 2726 controls the transmission module 2704to transmit a signal, e.g., a beacon signal, in accordance with theadjusted communications device transmission timing. When storedcommunication session state information 2758 indicates that anestablished session is ongoing, via session active flag 2760 being set,the transmission control module 2726 controls the transmission module2704 to repeat beacon signal portion transmission operations. Thetransmission control module 2726 controls the wireless terminal torepeat beacon signal portion transmission operation in both the inactiveand active modes of wireless terminal operation.

Communication session initiation module 2728 is used to controloperations to establish a communications session with another wirelessterminal, from which a beacon signal was received. For example,following a beacon signal detection, wherein the beacon signal issourced from another wireless terminal, if wireless terminal 2700desires to establish a communications session with said another wirelessterminal, module 2728 is activated to start to initiate thecommunication session, e.g., generating and processing handshakingsignals in accordance with a predetermined protocol.

Beacon detection control module 2730 controls the beacon signaldetection module 2720 operation. For example, when stored communicationsession state information 2758 indicates that an established session isongoing, via session active flag 2760 being set, the beacon detectioncontrol module 2730 controls the beacon signal detection module 2720 torepeat detection operations. The beacon detection control module 2730controls the wireless terminal to repeat beacon detection operations inboth the inactive and active modes of wireless terminal operation.

Timing adjustment module 2732 pseudo randomly adjusts the start of atleast one of a beacon transmission time period and a beacon receive timeperiod in a recurring sequence of such time periods. Pseudo random basedtiming offset 2752 is an output of timing adjustment module 2732. Timingadjustment module 2732 is, used to shift the wireless terminal's timingstructure with respect to other wireless terminals, operatingindependently, such as to increase the likelihood of the wirelessterminal and a peer being able to detect one another's presence whilelimiting beacon transmit and/or beacon detection time intervals.

Mode control module 2734 controls the communications device to operateduring different times, in a first and second mode of operation, inwhich the communications device transmits beacon signals. For example,the first mode of operation is an inactive mode in which thecommunications device transmits beacon signals, detects for beaconsignals, but is restricted from transmitting user data; the second modeof operation is an active mode in which the communications devicetransmits beacon signals, detects for beacon signals, and is permittedto transmit user data. Another mode of operation, into which modecontrol module 2734 can control the communications device to operate isa search mode in which the wireless terminal searches for beacon signalsbut is not permitted to transmit.

Beacon signal generation module 2736 generates beacon signal portions2748, e.g., beacon bursts including a least one beacon symbol, which aretransmitted by transmission module 2704. User data signal generationmodule 2738, generates user data signals 2774, e.g., signals conveyingcoded blocks of user data such as voice data, other audio data, imagedata, text data, file data, etc. User data signal generation module 2738is active when the wireless terminal is in active mode and the generateduser data signals 2774 are transmitted via transmission module 2704during time intervals reserved for user data transmit/receive signals.User data recovery module 2740 recovers user data from received userdata signals 2776 received from a peer in a communication session withwireless terminal 2700. The received user data signals 2776 are receivedvia receiver module 2702, while the wireless terminal is in an activemode of operation during time intervals reserved for user datatransmit/receive signals.

Duplex control module 2742 controls operation of duplex module 2703,e.g., controlling antenna 2705 to be coupled to receiver module 2702 forreceive time intervals, e.g., beacon monitoring time intervals andintervals for receiving user data, and to be coupled to transmissionmodule 2704 for transmission time intervals, e.g., beacon transmissiontime intervals and intervals for transmitting user data. Duplex controlmodule 2742 also controls at least some circuits in at least one ofreceiver module 2702 and transmission module 2704 to be powered downduring certain time intervals, thereby conserving battery power.

Data/information 2718 includes current mode information 2744, currenttime information 2746, generated beacon signal portion 2748, detectedbeacon flag 2750, pseudo random based timing offset 2752, detectedbeacon signal portion 2754, determined timing offset based on detectedbeacon signal portion 2756, communication session state information2758, timing structure information 2764, mode information 2768,generated user data signal 2774, and received user data signal 2776.

Current mode information 2744 includes information identifying thewireless terminal's current mode of operation, sub-modes and/or state ofoperation, e.g., whether the wireless terminal is in a mode where itreceives but does not transmit, whether the wireless terminal is aninactive mode including beacon signal transmission but not allowing userdata transmissions, or whether the wireless terminal is in an activemode including beacon signal transmissions and permitting user datatransmissions.

Current time information 2746 includes information identifying thewireless terminal time with respect to its position within a recurringtiming structure being maintained by the wireless terminal, e.g., anindexed OFDM symbol transmission time period within the structure.Current time information 2746 also includes information identifying thewireless terminal's time with respect to another timing structure, e.g.,of another wireless terminal or of a fixed location beacon transmitter.

Communication session state information 2758 includes a session activeflag 2760 and peer node identification information 2762. Session activeflag 2760 indicates whether or not the session is still active. Forexample, a peer node in a communication session with WT 2700 powersdown, the wireless terminal 2700 ceases to detect the peer's beaconsignal, and session active flag is cleared. Peer node identificationinformation 2762 includes information identifying the peer. In variousembodiments, the peer node ID information is conveyed, at least in part,via beacon signals.

Timing structure information 2764 includes information definingduration, ordering and spacing of various intervals such as, e.g.,beacon transmission intervals, beacon detection intervals, user datasignaling intervals and silence intervals. Timing structure information2764 includes intervals' timing relationship information 2766.Intervals' timing relationship information 2766 includes, e.g.,information defining: (i) that a beacon receive time period is longerthan a beacon transmission time period; (ii) that beacon receive andbeacon transmission time periods are non-overlapping; (iii) that thebeacon receive time period is at least two times the beacon transmittime period in duration; (iv) the silence period is at least twice oneof the beacon transmission time period and the beacon receive timeperiod.

Mode information 2768 includes initial search mode information 2769,inactive mode information 2770 and active mode information 2772. Initialsearch mode information 2769 includes information defining an initialextended duration search mode for beacon signals. The duration of theinitial search exceeds the expected interval between successive beaconburst transmissions by other wireless terminals which are transmittingsequences of beacon burst signals. The initial search mode information2769 is used for performing an initial search upon power up. Inaddition, in some embodiments the wireless terminal enters the initialsearch mode from the inactive mode occasionally, e.g., if no otherbeacon signals have been detected while in the inactive mode and/or ifthe wireless terminal wants to perform a faster and/or more thoroughbeacon search than is achieved using the inactive mode. Inactive modeinformation 2770 defines an inactive mode of wireless terminal operationincluding a beacon signal interval, a beacon monitoring interval and asilence interval. Inactive mode is a power saving mode where thewireless terminal conserves energy in the silence mode, yet is able toindicate its presence by the beacon signal and is able to maintainsituational awareness of the presence of other wireless terminals by alimited duration beacon monitoring interval. Active mode information2772 defines an active mode of wireless terminal operation including abeacon signal transmission interval, a beacon monitoring interval, auser data TX/RX interval, and a silence interval.

FIG. 28 is a drawing 2800 illustrating an exemplary time line, sequenceof events, and operations with respect to two wireless terminals in anad hoc network which become aware of the presence of each other andachieve timing synchronization via the use of wireless terminal beaconsignals. Horizontal axis 2801 represents a time line. At time 2802,wireless terminal 1 powers on and starts an initial monitoring forbeacon signals, as indicated by block 2804. The monitoring continuesuntil time 2806, at which point wireless terminal completes its initialsearch, with the result that no other wireless terminals were found;then, wireless terminal 1 enters an inactive mode of operation includingrepetitions of beacon transmission intervals in which wireless terminal1 transmits a beacon signal burst, beacon monitoring intervals in whichthe wireless terminal monitors for beacon signals, and silence intervalsin which the wireless terminal neither transmits nor receives, thusconserving power, as illustrated by block 2808.

Then, at time 2810, wireless terminal 2 powers on and starts initialbeacon monitoring as indicated by block 2812. Then, at time 2814,wireless terminal 2 detects a beacon signal from wireless terminal 1,decides that it seeks to establish a communication session with wirelessterminal 1, and determines a time offset such that wireless terminalwill receive a beacon signal burst from wireless terminal 2 during awireless terminal 1 beacon monitoring interval, as indicated by block2815.

At time 2816, wireless terminal 2 has entered active mode which includesrepetitions of: beacon transmission intervals, beacon monitoringintervals, and user data intervals, and at time 2816 wireless terminal 2transmits a beacon signal in accordance with the determined time offsetof step 2815, as indicated by block 2818. Then wireless terminal 1detects the beacon signal from wireless terminal 2 and switches toactive mode as indicated by block 2820.

Between time interval 2816 and 2824 wireless terminal 1 and wirelessterminal 2 exchange signals to establish a communications session andthen participate in the session exchanging user data, as indicated byblock 2822. In addition, during this time interval beacon signalsreceived during the session are used to update timing and maintainsynchronization. Wireless terminal 1 and wireless terminal 2 may be, andsometimes are, mobile nodes which can be moving during thecommunications sessions.

At time 2824, wireless terminal 1 powers down, as indicated by block2826. Then, at time 2828, wireless terminal 2 determines that signal hasbeen lost from wireless terminal 1 and the wireless terminal transitionsto an inactive mode, as indicated by block 2830. Signal can also be, andsometime is, lost due to other conditions, e.g., wireless terminals 1and 2 moved far enough away from each other such that the channelconditions were insufficient to maintain the session.

Sequence of arrows 2832 illustrates wireless terminal 1 beacon signalbursts, while sequence of arrows 2834 illustrates wireless terminal 2beacon signal bursts. It should be observed that the timing between thetwo wireless terminals has been synchronized, as a function of areceived beacon signal from wireless terminal 1, such that wirelessterminal 1 is able to detect a beacon signal burst from wirelessterminal 2, during its beacon signal monitoring interval.

In this example, a wireless terminal, which has powered up, performsmonitoring during an initial beacon monitoring period until a beacon isdetected or until the initial beacon monitoring period expires,whichever comes first. The initial beacon monitoring period is, e.g., anextended duration monitoring period having a duration which exceeds oneiteration including a beacon transmission interval. In this example, theinitial beacon monitoring period is performed prior to entering a modein which beacon signals are transmitted. A wireless terminal in aninactive mode, said inactive mode including beacon transmissionintervals, beacon monitoring intervals and silence intervals,occasionally enters a long duration beacon monitoring interval, e.g., tocover a corner case condition in which two wireless terminals shouldhappen to start up simultaneously.

In some other embodiments, a wireless terminal enters an inactive mode,said inactive mode including beacon transmission intervals and limitedduration beacon monitoring intervals following power on without firsthaving an extended beacon monitoring interval. In some such embodiments,a wireless terminal may, and sometimes does, perform pseudo-random timeshifts while searching for other beacon signals to facilitate alignmentbetween its own beacon monitoring intervals and other wireless terminalbeacon transmission intervals.

Drawing 2900 of FIG. 29 illustrates exemplary synchronized timingbetween two wireless terminals based on beacon signals in accordancewith an exemplary embodiment. Drawing 2902 illustrates timing structureinformation with respect to wireless terminal 1, while drawing 2904includes timing structure information with respect to wireless terminal2. Drawing 2900 may correspond to FIG. 28 after the wireless terminalshave been timing synchronized, e.g., based on wireless terminal 2detecting a beacon signal from wireless terminal 1. Drawing 2902includes a wireless terminal 1 beacon transmission interval 2906, awireless terminal 1 beacon receive time interval 2908, a wirelessterminal 1 user data TX/RX interval 2910 and a WT 1 silence interval2912. Drawing 2904 includes a wireless terminal 2 beacon transmissioninterval 2914, a wireless terminal 2 beacon receive time interval 2916,a wireless terminal 2 user data TX/RX interval 2918 and a WT 2 silenceinterval 2920. It should be observed that wireless terminal 2 hasadjusted its timing such that when it transmits a beacon signal burstduring WT 2 beacon transmit interval 2914, WT 1 will receive the beaconsignal burst during its beacon receive interval 2908. It should also beobserved that there is an overlapping portion of the user data TX/RXregions 2922 which can be used for user data signaling. This approachmaintains the same basic timing structure for different wirelessterminals, and uses a determined timing shift of one of the wirelessterminal's timing to achieve synchronization.

Drawing 3000 of FIG. 30 illustrates exemplary synchronized timingbetween two wireless terminals based on beacon signals in accordancewith another exemplary embodiment. Drawing 3002 includes timingstructure information with respect to wireless terminal 1, while drawing3004 includes timing structure information with respect to wirelessterminal 2. Drawing 3000 may correspond to FIG. 28 after the wirelessterminals have been timing synchronized, e.g., based on wirelessterminal 2 detecting a beacon signal from wireless terminal 1. Drawing3002 includes a wireless terminal 1 beacon receive interval 3006, awireless terminal 1 beacon transmission interval 3008, a wirelessterminal 1 beacon receive time interval 3010, a wireless terminal 1 userdata TX/RX interval 3012 and a WT 1 silence interval 3014. Drawing 3004includes, a wireless terminal 2 beacon receive interval 3016, a wirelessterminal 2 beacon transmission interval 3018, a wireless terminal 2beacon receive time interval 3020, a wireless terminal 2 user data TX/RXinterval 3022 and a WT 2 silence interval 3024. It should be observedthat wireless terminal 2 has adjusted its timing such that when ittransmits a beacon signal burst during WT 2 beacon transmit interval3018, WT 1 will receive the beacon signal burst during its beaconreceive interval 3010. It can also be observed that, in this embodiment,following wireless terminal 2's timing adjustment, wireless terminal 2receives a beacon burst transmitted by wireless terminal 1 duringwireless terminal 1 beacon transmission interval 3008 during its beaconreceive interval 3016. It should also be observed that there is anoverlapping portion of the user data TX/RX regions 3026 which can beused for user data signaling. This approach maintains the same basictiming structure for different wireless terminals, and uses a determinedtiming shift of one of the wireless terminal's timing to achievesynchronization, and both wireless terminals are able to receive beaconsignal bursts from each other, on an ongoing basis followingsynchronization.

Drawing 3100 of FIG. 31 illustrates exemplary synchronized timingbetween two wireless terminals based on beacon signals in accordancewith another exemplary embodiment. Drawing 3102 includes timingstructure information with respect to wireless terminal 1, while drawing3104 includes timing structure information with respect to wirelessterminal 2. Drawing 3100 may correspond to FIG. 28 after the wirelessterminals have been timing synchronized, e.g., based on wirelessterminal 2 detecting a beacon signal from wireless terminal 1. Drawing3102 includes a wireless terminal 1 beacon transmission interval 3106, awireless terminal 1 beacon receive time interval 3108, a wirelessterminal 1 user data TX/RX interval 3110 and a WT 1 silence interval3112. Drawing 3104 includes a wireless terminal 2 beacon transmissioninterval 3114, a wireless terminal 2 beacon receive time interval 3116,a wireless terminal 2 user data TX/RX interval 3118 and a WT 2 silenceinterval 3120. It should be observed that wireless terminal 2 hasadjusted its timing such that when it transmits a beacon signal burstduring WT 2 beacon transmit interval 3116, WT 1 will receive the beaconsignal burst during its beacon receive interval 3108. It can also beobserved that, in this embodiment, following wireless terminal 2'stiming adjustment, wireless terminal 2 receives a beacon bursttransmitted by wireless terminal 1 during wireless terminal 1 beacontransmission interval 3106 during its beacon receive interval 3114. Itshould also be observed that user data TX/RX intervals 3110, 3118overlap. This approach uses a different timing structure for the twowireless terminals, e.g., the wireless terminal which performed thefirst detection of the other beacon and adjusts its internal timing,e.g., WT 2, uses the interval ordering of drawing 3104. In some suchcases, upon wireless terminal 2 ending the communications session andentering an inactive state including beacon signal transmission wirelessterminal 2 goes to the ordered timing sequence represented by FIG. 3102.

FIG. 32 includes drawings 3200 and 3250 depicting exemplary transmissionblocks according to another embodiment. Although depicted and describedherein as separate transmission blocks, the transmissions blocks ofdrawings 3200 and 3250 may be considered together as a singletransmission block in some embodiments, e.g., where the transmissionblocks are contiguous with one another. According to the embodimentdepicted in FIG. 32, a robust scheme for information exchange in a peerto peer network is provided, which is particularly beneficial forhalf-duplex wireless terminals. For example, the technique describedherein may used to enhance the operation of peer detection and discoverydiscussed above. The technique described herein may also be used toenhance data exchange for other communications, including userscheduling and orthogonal connection ID generation, among others.

Drawing 3200 depicts a first transmission block interval 3208 anddrawing 3250 depicts second transmission block interval 3258, wherelegend 3202 corresponds to drawing 3200 and legend 3252 corresponds todrawing 3250, and where vertical axes 3204 and 3254 represent thefrequency, e.g., OFDM tone, index and horizontal axes 3206 and 3256represent the transmission unit time index within the transmission blockintervals 3208 and 3258, respectively.

In accordance with the embodiment shown in FIG. 32, each wirelessterminal is configured to transmit at least two tones over two differenttime symbols (or transmission unit time indices), where, at most, one ofthe two transmissions share the same time symbol (or transmission unittime index). Referring to drawing 3200, Wireless Terminal A transmits afirst transmission symbol represented by WT A transmission block 3210,such as a beacon symbol, with a frequency index=5 and a time index=1during first transmission block interval 3208, and a second transmissionsymbol represented by WT A transmission block 3260, with a frequencyindex=1 and a time index=5 during second transmission block interval3258. The first transmission symbol and the second transmission symbolcarry the data or information, such as the beacon data, for example.Similarly, Wireless Terminal B transmits a first transmission symbolrepresented by WT B transmission block 3212, with a frequency index=7and a time index=1 during first transmission block interval 3208, and asecond transmission symbol represented by WT B transmission block 3262,with a frequency index=1 and a time index=7 during second transmissionblock interval 3258. As illustrated by this example, WT A will be ableto receive the information carried by second transmission symbol 3262 ofWT B even though it was unable to receive first transmission symbol 3212of WT B (since WT A was transmitting its first transmission symbol 3210at that same time index). Likewise, WT B will be able to receive theinformation carried by second transmission symbol 3260 of WT A eventhough it was unable to receive first transmission symbol 3210 of WT A.

As another example, FIG. 33 includes drawings 3300 and 3350 depictingexemplary transmission blocks according to another embodiment includingthree wireless access terminals A, B and C. As with the techniquedescribed above in conjunction with FIG. 32, the technique describedherein may be used to enhance data exchange for other communications,including user scheduling and orthogonal connection ID generation, amongothers. As discussed above, although depicted and described herein asseparate transmission blocks, the transmissions blocks of drawings 3300and 3350 may be considered together as a single transmission block insome embodiments, e.g., where the transmission blocks are contiguouswith one another.

Drawing 3300 depicts first transmission block interval 3308 and drawing3350 depicts second transmission block interval 3358, where legend 3302corresponds to drawing 3300 and legend 3352 corresponds to drawing 3350,and where vertical axes 3304 and 3354 represent the frequency, e.g.,OFDM tone, index and horizontal axes 3306 and 3356 represent thetransmission unit time index within the transmission block intervals3308 and 3358, respectively.

In accordance with the embodiment shown in FIG. 33, each wirelessterminal is configured to transmit at least two tones over two differenttime symbols (or transmission unit time indices), where, at most, one ofthe two transmissions share the same time symbol (or transmission unittime index). Referring to drawing 3300, Wireless Terminal A transmits afirst transmission symbol represented by WT A transmission block 3310,such as a beacon symbol, with a frequency index=3 and a time index=1during first time interval 3308, and a second transmission symbolrepresented by WT A transmission block 3360, with a frequency index=1and a time index=3 during second transmission block interval 3358. Thefirst transmission symbol and the second transmission symbol carry thedata or information, such as the beacon data, for example. Similarly,Wireless Terminal B transmits a first transmission symbol represented byWT B transmission block 3312, with a frequency index=3 and a timeindex=3 during first time interval 3308, and a second transmissionsymbol represented by WT B transmission block 3362, with a frequencyindex=3 and a time index=3 during second transmission block interval3358. Wireless Terminal C transmits a first transmission symbolrepresented by WT C transmission block 3314, with a frequency index=7and a time index=3 during first time interval 3308, and a secondtransmission symbol represented by WT C transmission block 3364, with afrequency index=3 and a time index=7 during second transmission blockinterval 3358.

As illustrated by the example of FIG. 33, WT A is able to receive theinformation carried by first transmission symbol 3312 of WT B eventhough it will not be able to receive second transmission symbol 3362 ofWT B (since WT A is transmitting its second transmission symbol 3360 atthat same time index=3). WT A is able to receive first and secondtransmission symbols 3314 and 3364 of WT C.

Continuing with FIG. 33, WT B is able to receive the information carriedby first transmission symbol 3310 of WT A even though it will be unableto receive second transmission symbol 3360 of WT A. WT B will be able toreceive the information carried by second transmission symbol 3364 of WTC even though it was unable to receive first transmission symbol 3314 ofWT C. WT C is able to receive first and second transmission symbols 3310and 3360 of WT A. WT C will be able to receive the information carriedby second transmission symbol 3362 of WT B even though it was unable toreceive first transmission symbol 3312 of WT B.

In the above described examples of FIGS. 32 and 33, the wirelessterminal is configured to transmit at least two tones over two differenttime symbols (or transmission unit time indices), where, at most, one ofthe two transmissions share the same time symbol (or transmission unittime index) by transposing the frequency index and the time indexbetween the first transmission block interval and the secondtransmission block interval, such that first transmission symbolcorresponds to position (i, j) and the second transmission symbolcorresponds to position (j, i). Other algorithms may be employed inalternative embodiments to satisfy the requirement that, at most, one ofthe two transmissions share the same time symbol, including the firstand second block can be interleaved in time, or the rows of each blockcan be permutated in an arbitrary fashion, for example.

It is noted that the technique described in conjunction with FIGS. 32and 33 increases overhead by sending duplicate information in first andsecond transmission block intervals. However, the technique provides thedesirable robustness by greatly improving the likelihood of informationexchange in peer to peer systems. Thus, the ability to exchange beaconssignals, user scheduling data and the like is significantly improved,thereby improving device detection and discovery and user trafficscheduling and the overall user experience. Another benefit provided bythe technique described in conjunction with FIGS. 32 and 33 is that thedesensing (noise interference) probability is decreased since a devicewill share positions with two different set of neighbors in two blocks,a first neighbor in the first transmission block interval and adifferent second neighbor in the second transmission block interval.

In accordance with another embodiment, the logic for assigning frequencyand time slot assignments (also referred to as “time symbols” and “timeindices”) for information exchange in a peer to peer network isdescribed in conjunction with drawings 3400 of FIGS. 34 and 3500 of FIG.35. In FIG. 34, vertical axis 3404 represents K nodes within a wirelessnetwork and horizontal axis 3406 represents the time slots T needed tosatisfy the following criteria for every pair of half-duplex nodes (Aand B) within K nodes:

(1) At least once, A transmits and B is silent; and

(2) At least once, B transmits and A is silent.

As discussed above, satisfying the above criteria for half-duplex nodesfor information exchange enhances the operation of peer detection anddiscovery, for example. The technique described herein may also be usedto enhance data exchange for other communications, including userscheduling and orthogonal connection ID generation, among others.

If the number of frequency resources (e.g., orthogonal tones in the caseof beacon-type of signals are used) available are represented by N_(f),where N_(f)≧2, it can be shown that the number of time slots T needed tosatisfy the criteria defined above is at least:T≧(2K/N _(f))  Eq (1).

In the special case where K=N_(f) (as discussed above in conjunctionwith FIGS. 32 and 33), the lower bound of Eq. 1 can be expressed as:T=2√{square root over (K)}  Eq. (2).

In other words, the scheme shown in FIGS. 32 and 33 achieves the leastpossible number of time symbols required to complete the messageexchange and is thus optimal in this special case.

In a more general case, however, K may or may not be equal to N_(f). Thebound shown in Eq. 1 is not necessarily tight. The consideration of timeslot assignment in this more general case follows.

According to one embodiment, and in order to reduce the number of timesslots for transmission while achieving the conditions identified abovefor information exchange, each node transmits half of the time. Forexample, the assignment of time slots to each node is made employingequal-weight binary words or “equal weight codewords” where the numberof slots assigned to a half-duplex node for transmission of exchangeinformation is (T/2). According to one embodiment, the time slots T*needed to satisfy the criteria defined above for information exchange ofhalf-duplex nodes (A and B) of K nodes employing equal weight binarywords is given by:

$\begin{matrix}{T^{*} = {\min\{ l \middle| {\begin{pmatrix}l \\\lfloor {l\text{/}2} \rfloor\end{pmatrix} \geq K} \}}} & {{Eq}.\mspace{14mu}(3)}\end{matrix}$where l represents the number of time slots, and K represent then numberof nodes.

For, example, in a case where K=20, Eq. 3 yields T*=6. By way ofillustration, if T*=6, equal-weight binary words time slot assignmentsto node “3” and node “6” in FIG. 34 can be represented by assignments3410 an 3412, respectively, where the weight is (T*/2)=3. In assignment3410, node “3” is shown as being assigned slots 2, 3 and 4. Inassignment 3412, node “6” is assigned slots 3, 4 and 5. During theseassigned time slots, the node transmits at least a portion of similarinformation for the purpose of information exchange with the other nodesof the network.

FIG. 35 depicts table 3500 including an exemplary configuration of timeassignments for 20 nodes (or users) where each node is assigned 3 timesymbols to transmit its signal. Vertical index 3504 represents deviceIDs, and horizontal index 3506 defines the time slots (or time indices)assigned to each device ID. In one embodiment, table 3500 is stored inall the nodes, and when a node joins the network, the device canascertain the set of time indices assigned to it based on its ID. In oneexample, the device can obtain its ID, which is typically unique withina particular neighborhood, upon joining the network. According toanother example, the node can deterministically obtain its ID within aknown device ID space without communicating to other nodes already inthe network. It is noted that FIG. 35 does not contain the frequencyassignment to the nodes. For CDMA networks, the nodes assigned to thesame symbol transmit their signal over the total bandwidth usingdifferent spreading signatures, such as Walsh codes, for example. Inthis special case, there are up to three nodes transmittingsimultaneously for any time symbol. For OFDM networks, the nodes canselect orthogonal frequency resources which can be based on their ID andis stored in a time-to-frequency assignment table. By way ofillustration, FIG. 36 depicts exemplary table 3600 identifying the timeand frequency resource assignments based on exemplary table 3500 of FIG.35 according to one embodiment. In table 3600, vertical axis 3604defines the frequency, e.g., OFDM tone, index and horizontal axis 3606represents the transmission unit time index. It is noted that thepopulation of table 3600 from table 3500 is only illustrative, and othertechniques for mapping the ID and time assignments of table 3500 to thetime-to-frequency assignments of table 3600 may be used. Device ID 1 oftable 3500 is assigned time slot 4, 5 and 6. In table 3600, device ID 1is assigned frequency index 0 and time slots 4, 5 and 6. In FIG. 35,device ID 2 of table 3500 is assigned time slot 3, 5 and 6. In table3600, device ID 2 is assigned frequency index 0 for time slot 3;however, frequency index 0 is already assigned to device ID 1 for timeslots 5 and 6. Accordingly, device ID 2 is assigned the next availablefrequency index, i.e., frequency index 1 for time slots 5 and 6 in table3600. In FIG. 35, device ID 3 of table 3500 is assigned time slot 2, 5and 6. In table 3600, device ID 3 is assigned frequency index 0 for timeslot 2; however, frequency index 0 is already assigned to device ID 1for time slots 5 and 6 and frequency index 1 is already assigned todevice ID 2 for time slots 5 and 6. Accordingly, device ID 3 is assignedthe next available frequency index, i.e., frequency index 2 for timeslots 5 and 6 in table 3600. The remaining device IDs 4-20 are similarlymapped to table 3600.

In this particular embodiment, the number of resources (e.g., orthogonaltones) required by the network is K/2, (K=6) where T* is an even value,and K=

$\begin{pmatrix}T^{*} \\\lfloor {T^{*}\text{/}2} \rfloor\end{pmatrix}.$Thus, in certain embodiments, the schedule can be modified or definedsuch that at most [K/2] tones are used for any K nodes in the wirelessnetwork.

In certain embodiments, the number of tones can be further reduced byselecting binary works of weight less than [T*/2] to thereby reduce thenumber of frequency resources required. By way of example, in the casewhere K=84 nodes are to be supported, Eq. 3 yields T*=9 slots, assumingno constraint on N_(f). In the approach employing equal-weight binarywords, each node would be assigned a unique set of 4 time slots fortransmission, and the number of resources (N_(f)) required is at least42 tones. By reducing the number of time slots to only 3 slots in thisparticular case, the network would be able to accommodate

$\begin{pmatrix}9 \\3\end{pmatrix} = 84$nodes, requiring only

$\begin{pmatrix}8 \\2\end{pmatrix} = 28$tones.

By adjusting the choice of weight of the codewords, i.e., the number oftransmissions assigned to each user, the number of time slots requiredto finish the process of information exchange can be balanced with thenumber of tones (or units of frequency resource) required. For examplein one embodiment, each node is permitted to transmit once, and, thus, Ktime slots (or time symbols) are required. In contrast, according toanother embodiment, each node may transmit with half-rate code, wherethe number of time slots (or time symbols) is minimized and given by Eq.3. Thus, a generalized formula for T can be given by:

$\begin{matrix}{{T( {K,N_{f}} )} = {\min\{ l \middle| {\begin{pmatrix}l \\\lfloor {l\; N_{f}\text{/}K} \rfloor\end{pmatrix} \geq K} \}}} & {{Eq}.\mspace{14mu}(4)}\end{matrix}$

According to Eq. 4, selection of a codeword weight approximately equalto (N_(f)/K) yields an efficient allocation of resources.

While described in the context of an OFDM TDD system, the methods andapparatus of various embodiments are applicable to a wide range ofcommunications systems including many non-OFDM, many non-TDD systems,and/or many non-cellular systems.

In various embodiments nodes described herein are implemented using oneor more modules to perform the steps corresponding to one or moremethods, for example, generating a beacon signal, transmitting a beaconsignal, receiving beacon signals, monitoring for beacon signals,recovering information from received beacon signals, determining atiming adjustment, implementing a timing adjustment, changing a mode ofoperation, initiating a communication session, etc. In some embodimentsvarious features are implemented using modules. Such modules may beimplemented using software, hardware or a combination of software andhardware. Many of the above described methods or method steps can beimplemented using machine executable instructions, such as software,included in a machine readable medium such as a memory device, e.g.,RAM, floppy disk, etc. to control a machine, e.g., general purposecomputer with or without additional hardware, to implement all orportions of the above described methods, e.g., in one or more nodes. Inone or more exemplary embodiments, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by acomputer. By way of example, and not limitation, such computer-readablemedia can comprise RAM, ROM, EEPROM, CD-ROM or other electronic storage,optical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code in the form of instructions or data structures and that canbe accessed by a computer. Also, any connection is properly termed acomputer-readable medium. For example, if the software is transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), or otherwireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk, high definition DVD (HD-DVD) and blue-ray disc,where disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combination of the above should also beincluded within the scope of computer-readable media.

Numerous additional variations on the methods and apparatus describedabove will be apparent to those skilled in the art in view of the abovedescriptions. Such variations are to be considered within scope. Themethods and apparatus of various embodiments may be, and in variousembodiments are, used with CDMA, orthogonal frequency divisionmultiplexing (OFDM), and/or various other types of communicationstechniques which may be used to provide wireless communications linksbetween access nodes and mobile nodes. In OFDM systems, the signals arenot necessarily restricted to beacon-type of signals. They can occupyany number of frequency resources which is at least determined by theamount of information contained in the signal. In some embodiments theaccess nodes are implemented as base stations which establishcommunications links with mobile nodes using OFDM and/or CDMA. Invarious embodiments the mobile nodes are implemented as notebookcomputers, personal data assistants (PDAs), or other portable devicesincluding receiver/transmitter circuits and logic and/or routines, forimplementing the methods of various embodiments.

What is claimed is:
 1. A wireless communications device comprising: aprocessor coupled to a memory and a wireless communications interface,said memory including information relating a plurality of deviceidentifiers to corresponding stored sets of time indices, each deviceidentifier in said plurality of device identifiers corresponding to adifferent stored set of time indices, each of the different stored setsof time indices including multiple time indices, said time indicescorresponding to symbol transmission times, sets of time indicescorresponding to different device identifiers differing by at least onetime index; the processor configured to transmit a first transmissionsymbol at a symbol transmission time corresponding to a first time indexfrom a first set of time indices corresponding to a first deviceidentifier being used by said communications device; the processorconfigured to transmit a second transmission symbol at a second symboltransmission time corresponding to a second time index from the firstset of time indices, the second time index being different from thefirst time index, a portion of the first transmission symbol and aportion of the second transmission symbol communicating the sameinformation.
 2. The wireless communications device of claim 1 whereinthe second time index included in the first set is not contained in asecond set of time indices associated with a second device identifier,the second set including at least one time index not contained in thefirst set.
 3. The wireless communications device of claim 2, whereinsaid second set of time indices associated with the second deviceidentifier includes a time index included in said first set; and whereinsaid information relating a plurality of device identifiers tocorresponding stored sets of time indices includes a table that maps thefirst device identifier to the first set of time indices and the seconddevice identifier to the second set of time indices.
 4. The wirelesscommunications device of claim 2 wherein the processor executes afunction to map the first device identifier to the first set of timeindices and the second device identifier to the second set of timeindices.
 5. The wireless communications device of claim 3 wherein theprocessor executes a module that determines a current device identifierused by the device at the present time to be one of at least the firstand the second device identifier, maps the current device identifier toone of at least the first and the second sets of time indices, andtransmits a transmission symbol at a time index from the mapped set oftime indices.
 6. The wireless communications device of claim 2, whereinthe first set of time indices and the second set of time indices are ofthe same size; and wherein the first and second sets of time indicesinclude more time indices which are the same than which are different.7. The wireless communications device of claim 2 wherein the first setof time indices has a size equal to the closest integer to half of thesize of a transmission block interval for communicating the first andsecond transmission symbols.
 8. The wireless communications device ofclaim 1 wherein the first transmission symbol is modulated in one of aCDMA waveform and an OFDM waveform.
 9. The wireless communicationsdevice of claim 1 wherein the first transmission symbol is modulated ina CDMA waveform and the size of the first set of time indices isdetermined by the size of the device identifier space and the maximumnumber of CDMA waveforms supportable in a given time index.
 10. Thewireless communications device of claim 1 wherein the first transmissionsymbol is modulated in an OFDM waveform.
 11. The wireless communicationsdevice of claim 1 wherein the processor is further configured to:transmit the first transmission symbol at a first frequencycorresponding to a first frequency index; transmit the secondtransmission symbol at a second frequency corresponding to a secondfrequency index, said second frequency being different from the firstfrequency.
 12. The wireless communications device of claim 11, whereinthe first frequency index =i, the first time index =j, the secondfrequency index =j, the second time index =i.
 13. The wirelesscommunications device of claim 1, wherein first transmission symbol andthe second transmission symbol is one of a beacon signal and a userscheduling signal.
 14. A method for operating a portable wirelessterminal comprising: storing in memory information relating a pluralityof device identifiers to corresponding stored sets of time indices, eachdevice identifier in said plurality of device identifiers correspondingto a different stored set of time indices, each of the different storedsets of time indices including multiple time indices, said time indicescorresponding to symbol transmission times, sets of time indicescorresponding to different device identifiers differing by at least onetime index; transmitting a first transmission symbol at a symboltransmission time corresponding to a first time index from a first setof time indices corresponding to a first device identifier being used bysaid portable wireless terminal; transmitting a second transmissionsymbol at a second symbol transmission time corresponding to a secondtime index from the first set of time indices, the second time indexbeing different from the first time index, a portion of the firsttransmission symbol and a portion of the second transmission symbolcommunicating the same information.
 15. The method of claim 14 whereinthe second time index included in the first set is not contained in asecond set of time indices associated with a second device identifier,the second set including at least one time index not contained in thefirst set.
 16. The method of claim 15, wherein said second set of timeindices associated with the second device identifier includes a timeindex included in said first set; and wherein said information relatinga plurality of device identifiers to corresponding stored sets of timeindices includes a table that maps the first device identifier to thefirst set of time indices and the second device identifier to the secondset of time indices.
 17. The method of claim 15 further comprising:executing a function to map the first device identifier to the first setof time indices and the second device identifier to the second set oftime indices.
 18. The method of claim 15, wherein the first set of timeindices and the second set of time indices are of the same size; andwherein the first and second sets of time indices include more timeindices which are the same than which are different.
 19. The method ofclaim 15 wherein the first set of time indices has a size equal to theclosest integer to half of the size of a transmission block interval forcommunicating the first and second transmission symbols.
 20. The methodof claim 14 wherein the first transmission symbol is modulated in a CDMAwaveform and the size of the first set of time indices is determined bythe size of the device identifier space and the maximum number of CDMAwaveforms supportable in a given time index.
 21. The method of claim 14wherein the first transmission symbol is modulated in an OFDM waveform.22. The method of claim 14 further comprising: transmitting the firsttransmission symbol at a first frequency corresponding to a firstfrequency index; transmitting the second transmission symbol at a secondfrequency corresponding to a second frequency index, said secondfrequency being different from the first frequency.
 23. The method ofclaim 22 wherein the first frequency index =i, the first time index =j,the second frequency index =j, the second time index =i.
 24. A portablewireless terminal comprising: means for storing information relating aplurality of device identifiers to corresponding stored sets of timeindices, each device identifier in said plurality of device identifierscorresponding to a different stored set of time indices, each of thedifferent stored sets of time indices including multiple time indices,said time indices corresponding to symbol transmission times, sets oftime indices corresponding to different device identifiers differing byat least one time index; and means for transmitting a first transmissionsymbol at a first time index from a first set of time indices and fortransmitting a second transmission symbol at a second time indexdifferent from the first time index from the first set of time indices,a portion of the first transmission symbol and a portion of the secondtransmission symbol including the same data.
 25. A computer programproduct, comprising: non-transitory computer-readable medium comprising:stored information relating a plurality of device identifiers tocorresponding stored sets of time indices, each device identifier insaid plurality of device identifiers corresponding to a different storedset of time indices, each of the different stored sets of time indicesincluding multiple time indices, said time indices corresponding tosymbol transmission times, sets of time indices corresponding todifferent device identifiers differing by at least one time index; codefor causing a computer in a portable wireless terminal to transmit afirst transmission symbol at a symbol transmission time corresponding toa first time index from a first set of time indices corresponding to afirst device identifier being used by the portable wireless terminal;code for causing the computer to transmit a second transmission symbolat a second symbol transmission time corresponding to a second timeindex different from the first time index, a portion of the firsttransmission symbol and a portion of the second transmission symbolcommunicating the same information.
 26. The method of claim 18, whereinsaid first and second sets of time indices each include three timeindices.
 27. The method of claim 18, wherein the first set of timeindices includes three time indices corresponding to three consecutivesymbol transmission time periods, the method further comprising:transmitting the same information during each of said three consecutivesymbol transmission time periods corresponding to the three time indicesincluded in said first set of time indices.